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THE  UNIVERSITY 

OF  ILLINOIS 

LIBRARY 

NATURAL  HISTORY  SURVBY 


5705 

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U.  of/.  Library 


ILLINOIS   BIOLOGICAL 
MONOGRAPHS 

Vol.  V  April,  19 19  No.  2 


Editorial  Committee 


Stephen  Alfred  Forbes  William  Trelease 

Henry  Baldwin  Ward 


Published  tTNDER  the 

Auspices  of  the  Graduate  School  by 

THE  University  of  Illinois 


Copyright,  1920  by  the  University  of  Illinois 
Distributed  Jxjne  7, 1920. 


CONTRIBUTIONS  TO  THE  LIFE 

HISTORIES  OF  GORDIUSROBUS- 

TUS  LEIDY  AND  PARAGOR- 

DIUS  FARIUS  (LEIDY) 


WITH  TWENTY-ONE  PLATES 


BY 

HENRY  GUSTAV  MAY 


Contributions  from  the 

Zoological  Laboratory  of  the  University  of  Illinois 

under  the  direction  of  Henry  B.  Ward,  No.  144 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILMENT  OF  THE  REQUIREMENTS  FOR  THE  DEGREE 

OF  DOCTOR  OF  PHILOSOPHY  IN  ZOOLOGY  IN  THE  GRADUATE 

SCHOOL  OF  THE  UNIVERSITY  OF  ILLINOIS 

1917 


TABLE  OF  CONTENTS 

PAGES 

Introduction 7 

Material  and  Methods 10 

Observations  on  Gordius  robusius 16 

Determination  of  Species 16 

Habits  of  Adults 19 

Early  Development 21 

Parasitism 23 

Organogeny 29 

Metamorphosis , 29 

Derivation  of  Tissues 29 

Later  Development 31 

Observations  on  Paragordius  varius 44 

Determination  of  Species 44 

Habits  of  Adults 44 

Early  Development 45 

Parasitism 45 

Organogeny 47 

Discussion 56 

Biology 56 

Occurrence  and  Behavior  of  Adults 56 

Behavior  of  Larvae 59 

Infection  and  Intermediate  Host 59 

Developmental  Period 60 

Organogeny 60 

Metamorphosis 61 

Later  Development 62 

Physiology 68 

Nutrition 68 

Excretion 68 

Functions  of  Nervous  System 69 

Relationships 70 

Bibliography 72 

Explanation  of  Plates 76 


127]  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS— MAY 


INTRODUCTION 

The  Gordiacea  seem  to  have  escaped  the  observation  of  the  earlier 
writers  or  else  to  have  been  mistaken  for  filariae.  Meissner  (1856)  and 
Villot  (1874)  who  review  the  older  literature,  agree  that  the  first  reference 
to  the  group  was  made  by  Albert  the  Great.  Linnaeus  introduced  the 
term  Gordius  on  account  of  the  resemblance  of  a  mass  of  the  worms  to  the 
Gordian  knot.  He  included  in  the  genus  the  three  species  G.  aquaticus, 
argillaceus  and  medinensis ,  representing  respectively  the  present  families 
of  Gordiidae,  Mermithidae  and  Filariidae,  only  the  first  of  which  is  today 
retained  in  the  order  Gordiacea. 

Du  jar  din  was  the  first  to  give  detailed  descriptions  of  two  species, 
Gordius  aquaticus  and  Gordius  tolosanus,  and  to  point  out  the  difference 
between  Gordius  on  the  one  hand  and  Mermis  on  the  other. 

Von  Siebold  and  following  him  Meissner  (1855)  placed  Gordius  and 
Mermis  together  to  form  the  order  Gordiacea.  Meissner's  work  on 
the  anatomy  and  physiology  of  Gordius  and  Mermis  is  in  many  respects 
an  excellent  production  and  it  is  inconceivable  how,  after  such  observations, 
he  could  still  regard  the  two  groups  as  closely  related.  The  work  of  Gren- 
acher  (1868)  on  the  anatomy  of  Gordius  was  a  step  in  the  right  direction. 
He  emphasized  again  the  difference  between  Gordius  and  Mermis  and 
stated  that  the  two  could  not  possibly  belong  to  the  same  family. 

Villot  was  the  first  to  take  up  the  study  of  museum  specimens  and 
living  material  in  larger  quantities.  His  investigations  were  carried  on 
for  a  long  series  of  years  and  with  an  earnest  desire  to  solve  the  problems 
of  taxonomy,  physiology  and  life  history;  but  unfortunately  did  not  con- 
tribute much  to  a  clearer  knowledge  of  the  group.  The  problem  was  too 
great  for  the  methods  he  employed. 

In  England  Baird  described  several  species  and  in  Germany  von  Lin- 
stow  added  a  large  number  of  names  without  giving  descriptions  adequate 
for  identification. 

The  greatest  contributions  to  the  taxonomy  of  the  group  have  undoubt- 
edly been  made  by  Camerano,  chiefly  because  he  had  at  his  disposal  more 
material  than  has  ever  been  available  to  any  other  writer.  He  not  only 
described  a  large  number  of  species,  but  subdivided  the  group  into  several 
genera.  Creplin  (1847)  had  already  established  the  genus  Chordodes. 
Camerano  (1897)  carried  the  division  farther  in  separating  the  genera 
Paragordius  and  Parachordodes  from  the  genus  Gordius.  This  separation 
was  made  purely  on  external  characters.  Montgomery  in  a  paper  coming 
out  somewhat  later  also  established  a  genus  Paragordius  which,  so  far  as  the 
anatomy  of  the  forms  is  known,  includes  the  same  species  as  does  that  of 


8  ILLINOIS  BIOLOGICAL  MONOGRAPHS  {128 

Camerano,  but  is  founded  on  much  more  essential  characters.  That  the 
genus  has  found  universal  acceptance  is  perhaps  due  more  to  Montgomery's 
characterization  tljjn  to  that  of  Camerano.  The  genus  Parachordodes  has 
not  been  universally  accepted;  but  here  again  the  evidence  presented  in  this 
report  shows  that  the  characters  given  by  Cj^merano  are  accompanied  by 
others  which  indicate  a  natural  division  of  the  group.  He  characterizes 
Gordius  by  the  presence  of  a  postcloacal  ridge  in  the  male  and  the  absence  of 
true  areoles  on  the  cuticula,  Parachordodes  by  the  absence  of  postcloacal 
lidge  and  the  presence  of  areoles. 

In  America  several  species  were  described  by  Leidy,  but  most  of  the 
systematic  work  was  done  later  by  Montgomery.  Here  as  well  as  in  Europe 
little  more  than  pioneer  work  has  been  done.  Descriptions  and  identi- 
fications have  been  made  chiefly  from  preserved  material  and  isolated 
specimens  and  only  in  a  few  cases  from  living  material  collected  in  abim- 
dance. 

The  confusion  that  still  exists  in  the  group  is  due  in  a  large  measure  to 
the  fact  that  the  variations  within  a  species  are  very  great  while  the  differ- 
ences between  species  are  relatively  small.  When  isolated  and  often  poorly 
preserved  specimens  are  studied  it  is  natural  that  essential  characters  are 
often  overlooked  and  variations  are  taken  for  specific  characters.  This 
tends  on  the  one  hand  to  throw  species  together  and  on  the  other  to  separate 
members  of  a  single  species. 

The  two  characters  causing  the  most  confusion  are  size  and  color. 
Nearly  all  of  von  Linstow's  descriptions  include  besides  these  only  those 
that  are  common  to  nearly  all  Gordiacea.  Such  descriptions  are  useless. 
I  have  in  my  own  collection  specimens  of  a  single  species  ranging  in  length 
from  10  to  50  cm.  and  in  color  from  light  brown  to  nearly  black  and  others 
that  are  an  iridescent  gray.  Even  as  late  as  1910  Wesenberg-Lund  identi- 
fied specimens  as  Gordius  aquaiicus  on  account  of  their  size  and  made  the 
errors  that  I  shall  point  out  later. 

The  light  spots  in  the  cuticula  and  the  postcloacal  ridge  in  the  male  have 
been  taken  as  specific  characters,  and  the  species  bearing  either  has  usually 
without  hesitation  been  assigned  to  Gordius  aquaiicus.  The  ridge  certainly 
is  possessed  by  more  than  one  species  and  may  be  a  generic  character  while 
the  white  spots,  as  Montgomery  suspected,  are  due  to  physiological  con- 
ditions in  the  American  species  but  may  be  due  to  structures  in  the  hypo- 
derm  in  some  of  the  European  species. 

Altho  the  structure  of  the  cuticula  is  one  of  the  best  specific  characters, 
its  use  has  led  to  confusion  because  different  authors  have  studied  it  imder 
different  conditions  and  have  made  different  interpretations  of  what  they 
saw.  The  erroneous  theory  that  size,  color  and  cuticular  structures  change 
with  the  age  of  the  free  living  specimen  has  also  contributed  to  the  tangle. 


1291  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  9 

The  habits  of  different  species  are  practically  unknown.  Most  of  the 
material  has  been  found  accidentally  as  isolated  specimens  and  observations 
on  behavior  have  been  made  mostly  on  animals  in  captivity  as  Wesenberg- 
Lund  has  already  pointed  out.  The  scant  observations  made  on  animals 
in  nature  are  mostly  referred  to  the  group  as  a  whole  and  not  to  any  parti- 
cular species.  But  there  is  no  reason  for  supposing  that  the  habits  of 
different  species  are  the  same,  and  they  are  not  the  same  in  the  species 
forming  the  subject  of  this  paper. 

The  problem  of  the  life  history  of  the  group  has  attracted  much  atten- 
tion. Villot  at  one  time  thought  he  had  the  complete  cycle,  but  found  later 
that  he  had  to  modify  his  theories.  He  observed  the  embryological 
development,  the  encystment  of  the  larvae  in  a  large  number  of  animals, 
and  the  presence  of  nearly  adult  worms  in  beetles.  After  holding  for  a  long 
time  the  view  that  the  animals  harboring  the  encysted  larvae  were  inter- 
mediate hosts  he  finally  concluded  that  the  encysted  larvae  perish  and 
that  the  life  cycle  is  completed  in  some  other  way.  Camerano  indepen- 
dently arrived  at  the  same  conclusion.  Blunck  (1915)  again  speaks  of  an 
intermediate  host.  He  states  that  the  larvae  of  Gordius  tolosanus  penetrate 
soft-bodied  animals  and  these  in  turn  are  devoured  by  Dytiscus  larvae. 
Tadpoles  form  for  the  most  part  the  intermediate  host.  Development  is 
completed  in  Dytiscus  and  the  worms  escape  soon  after  the  beetle  emerges 
from  the  puparium.  The  facts  upon  which  these  deductions  are  based  are 
not  given.  Nothing  has  been  published  on  the  metamorphosis  or  the 
structure  of  the  early  parasite.  In  regard  to  the  later  organogeny  Villot 
(1891)  and  Vejdovsky  (1894)  have  supplied  the  only  information. 

The  adult  organization  is  better  known.  If  the  knowledge  of  it  is  still 
incomplete,  that  is  due  chiefly  to  the  fact  that  the  material  at  hand  has 
often  been  scarce  and  the  methods  employed  have  given  only  poor  results. 
Here  as  elsewhere  the  greatest  confusion  has  arisen  because  of  the  belief 
that  what  is  true  of  one  species  must  be  true  for  all.  Writers  have  not 
hesitated  to  denounce  their  fellow  workers  when  their  particular  species 
failed  to  show  what  others  had  found  in  very  different  species. 

This  very  brief  discussion  of  the  literature  on  Gordiacea  has  been  given 
not  with  the  purpose  of  presenting  an  historical  account  of  the  subject  but 
with  the  object  of  pointing  out  the  need  for  further  investigation  and  some 
of  the  difficulties  that  have  presented  themselves. 

The  present  investigation  was  undertaken  with  the  object  of  increasing 
the  knowledge  of  some  of  the  common  American  Gordiacea.  The  chief 
purpose  was  to  trace  out  if  possible  the  complete  life  cycle  in  one  or  the 
other  of  the  two  species  most  easily  available;  special  attention  being  given 
to  the  host  succession  and  the  organogeny. 

The  work  was  suggested  in  the  fall  of  1913  by  Professor  Henry  B. 
Ward,  under  whose  direction  it  was  carried  on.    To  him  I  wish  also  to  express 


10  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [130 

my  sincere  appreciation  for  a  keen  interest  in  the  work  and  for  many  helpful 
suggestions.  Professor  Ward  also  placed  at  my  disposal  his  library  and 
his  collection. 

Other  material  was  obtained  for  study  from  Harvard  University,  the 
University  of  California  and  the  University  of  Pennsylvania.  Doctor 
Minnie  Watson  Kamm  kindly  donated  an  infected  host  collected  in  the 
vicinity  of  Urbana  and  containing  valuable  material  of  Paragordius  varius. 

The  early  collections  were  made  under  the  direction  of  Professor  Frank 
Smith,  while  the  work  at  Douglas  Lake,  Michigan,  was  made  possible  thru 
the  kindness  of  the  director  of  the  station,  Doctor  H.  A.  Gleason,  and  was 
carried  on  under  the  direction  of  Doctor  W.  W.  Cort. 

Many  helpful  suggestions  were  obtained  from  Doctor  T.  B.  Magath  and 
other  workers  in  Professor  Ward's  laboratory. 

MATERIAL  AND  METHODS 

The  two  species  studied  are  Gordius  robustus  Leidy  1851  and  Paragor- 
dius varius  (Leidy  1851), 

Gordius  robustus  is  well  known  in  America;  its  range  extends  from  the 
Atlantic  to  the  Pacific.  It  is  by  far  the  most  abundant  species  in  the 
streams  near  Urbana,  Illinois,  and  is  occasionally  picked  up  in  collections 
made  for  the  zoological  laboratory  of  the  University  of  Illinois.  Eight 
males  and  one  female  were  collected  among  dead  grass  at  the  water's 
edge  in  a  small  stream  on  March  25,  1914.  Then,  for  nearly  a  month, 
diligent  searches  in  similar  localities  were  fruitless.  On  April  18  several 
more  specimens  were  found. 

It  was  noted  at  the  time  that  both  localities  were  at  the  edges  of  rapids. 
This  led  to  the  investigation  of  other  rapids  with  the  result  that  hundreds 
of  specimens  were  collected.  It  was  possible  to  walk  along  the  bank  of  a 
stream  and  descend  at  rapids  with  grassy  borders  and  collect  Gordius  in 
masses  containing  sometimes  as  many  as  25  or  50  worms.  Collections 
were  made  at  short  intervals  until  the  middle  of  June.  More  material  was 
collected  in  1915  and  1916. 

The  material  in  the  collection  of  Professor  Henry  B.  Ward  at  the  Uni- 
versity of  Illinois  was  available  for  study  as  well  as  Leidy's  specimens  of 
1879  and  the  material  from  the  collections  at  Harvard  University  and  the 
University  of  California. 

Eggs  were  found  thruout  the  month  of  May  and  the  larvae  hatched 
the  latter  part  of  May  and  during  June. 

Parasitic  stages  were  obtained  in  large  numbers  in  the  fall  of  1914  and 
again  in  1916.  Earlier  stages  were  obtained  by  infecting  the  hosts  in  the 
laboratory.  About  500  specimens  in  different  stages  of  development  were 
obtained  for  the  investigation. 

Paragordius  varius  is  even  more  abundant  than  the  previous  species  and 
is  the  one  most  commonly  collected  in  this  country. 


131]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  11 

Several  adults  of  this  species  were  collected  early  in  June  of  1914. 
Hundreds  of  specimens  were  obtained  at  Douglas  Lake,  Michigan,  during 
June,  July  and  August,  1915,  and  a  few  more  at  Urbana  in  the  spring  of 
1916,  Material  from  the  collections  mentioned  under  Gordius  robustus 
was  also  available. 

Eggs  and  larvae  were  obtained  in  large  numbers  wherever  adults  were 
found. 

Parasitic  stages  were  obtained  in  the  fall  of  1914  from  one  host  given 
to  me  by  Minnie  Watson  Kamm,  who  was  working  on  gregarines  in  this 
laboratory  at  that  time.  Abundant  material  was  obtained  in  all  but  the 
very  youngest  stages  in  the  summer  of  1915  at  Douglas  Lake.  Over  500 
specimens  were  available  for  study. 

The  ordinary  methods  used  in  anatomical  and  histological  study  were 
found  to  be  almost  useless  when  applied  to  the  study  of  the  Gordiacea  and 
special  methods  had  to  be  adapted  and  devised  at  nearly  all  stages  of  the 
investigations. 

The  study  of  living  material  was  confined  mostly  to  field  observations 
on  adults  and  hosts  and  to  the  study  of  the  embryonic  development  and 
larval  structure.  Nothing  is  gained  by  the  study  of  the  parasitic  forms  in 
the  living  condition. 

For  the  removal  of  parasites  from  the  hosts  it  was  necessary  to  use  a 
normal  salt  solution  of  full  strength  (0.75%).  Even  in  this  a  slight  injury 
usually  caused  a  flowing  out  of  part  of  the  body  contents.  In  pure  water 
the  specimens  rupture  at  short  intervals  all  along  the  body  almost  as  soon 
as  immersed.  This  applies  of  course  only  to  the  younger  stages  and  not 
to  those  that  have  already  formed  the  adult  cuticula.  The  specimens  were 
usually  removed  by  tearing  away  the  host  tissues  in  salt  solution  by  means 
of  fine  forceps  or  needles.  For  smaller  specimens  the  host  tissues  were 
teased  out  in  a  watch  glass  and  the  contents  examined  under  the  low 
power  of  a  microscope  at  a  magnification  of  about  100  diameters. 

The  problem  of  the  proper  killing  fluid  was  one  of  the  most  difl&cult  to 
solve,  and  in  part  has  not  yet  been  solved.  On  account  of  the  special 
methods  of  dehydration  and  imbedding  it  was  impossible  to  test  out  quickly 
the  action  of  any  particular  killing  fluid  and  on  account  of  the  short  seasons 
at  which  material  was  available  such  testing  could  usually  not  be  done 
during  the  collecting  season.  It  was  necessary  under  those  conditions  to 
use  the  rapidity  with  which  the  killing  fluid  acts  and  the  general  appearance 
of  the  killed  material  as  criteria.  Most  of  the  earlier  material  was  killed  in 
a  saturated  solution  of  corrosive  sublimate  to  which  from  five  to  ten  per 
cent  of  glacial  acetic  acid  had  been  added.  Later  this  solution  was  saturat- 
ed with  picric  acid  because  with  that  modification  it  killed  specimens  more 
quickly  and  prevented  to  a  great  extent  the  rupturing  of  the  parasitic 
forms  in  the  killing  fluid.     But  histological  preparations  show  that  this 


12  JLUNOIS  BIOLOGICAL  MONOGRAPHS  [132 

fluid  is  inferior  to  plain  corrosive  acetic.  Other  killing  fluids  tried  were  Flem- 
ming's  solution,  Zenker's  fluid,  Kleinenberg's  picro-sulphuric,  formalin 
and  other  less  known  fluids.  The  best  preparations  so  far  have  been 
obtained  with  corrosive  acetic  when  the  solution  was  used  at  a  temperature 
of  from  40  to  60°  C.  The  glycerol-alcohol  mixture  recommended  by  Looss 
for  killing  nematodes  yields  specimens  as  flat  as  ribbons  and  bearing  no 
resemblance  to  Gordiacea. 

For  killing  infected  hosts  the  solution  of  Camoy  and  Lebrun  consisting 
of  equal  parts  of  absolute  alcohol,  chloroform  and  glacial  acetic  acid  satur- 
ated with  corrosive  sublimate  was  found  to  give  very  excellent  results. 
It  could  not  be  used  for  killing  Gordiacea  because  it  made  the  material 
collapse  nearly  as  badly  as  did  the  glycerol-alcohol  mixture. 

The  methods  of  preparing  the  material  for  microscopic  study  were  more 
easily  devised  as  it  was  possible  to  take  up  this  problem  at  convenience. 
The  ordinary  methods  of  dehydration,  clearing  and  imbedding  were 
found  to  yield  nothing  but  flattened,  torn  and  distorted  preparations.  In 
delicate  specimens  at  certain  stages  a  sudden  increase  of  one  per  cent  in 
the  concentration  of  the  alcohol  caused  excessive  flattening  and  distortion. 
It  was  therefore  necessary  to  use  an  apparatus  for  insuring  the  gradual 
changing  of  the  liquids  in  dehydrating  and  clearing.  Several  devices  for 
this  purpose  have  been  introduced  by  European  workers.  The  one  best 
known  in  this  country  is  the  differentiator  introduced  by  N.  A.  Cobb  for 
making  microscopic  preparations  of  free  living  nematodes.  This  apparatus 
is  made  possible  by  the  fact  that  successive  layers  of  alcohol  of  increasing 
strengths  can  be  introduced  into  a  narrow  glass  tube  without  mixing.  By 
stirring  up  the  tube  a  little  it  is  possible  to  obtain  a  column  of  alcohol 
gradually  increasing  in  strength  from  the  bottom  upward.  If  the  specimen 
is  placed  in  the  bottom  of  the  tube  and  the  alcohol  permitted  to  ooze  out 
thru  a  capillary  point,  it  is  possible  to  draw  over  this  specimen  a  stream  of 
alcohol  of  gradually  increasing  strength. 

The  apparatus  used  for  this  work  depends  upon  a  slightly  different 
principle.  When  alcohol  is  introduced  at  the  bottom  of  a  broad  tube  filled 
with  alcohol  of  a  lower  strength  there  is  a  certain  amount  of  mixing  of  the 
two  liquids.  Such  a  tube  can  be  used  as  a  mixing  chamber.  The  essential 
parts  of  the  apparatus  used  consist  of  a  reservoir,  the  mixing  chamber  and 
the  specimen  chamber.  The  reservoir  is  a  tube  about  2  cm.  in  diameter 
and  25  cm.  long.  It  is  supplied  at  the  bottom  with  a  rubber  stopper  thru 
which  a  piece  of  small  glass  tubing  leads  nearly  to  the  bottom  of  the  mixing 
chamber.  The  best  results  are  obtained  when  this  glass  tube  is  drawn  out 
so  as  to  leave  an  opening  of  not  more  than  2  mm.  at  the  bottom.  The 
mixing  chamber  consists  of  a  piece  of  glass  tubing  about  1.5  cm.  wide  and 
5  cm.  long  supplied  at  each  end  with  a  perforated  rubber  stopper.  From 
the  bottom  of  this  chamber  a  piece  of  narrow  glass  tubing  leads  to  the  top 


133]  LIFE  HISTOR Y  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  13 

of  the  specimen  chamber.  This  tube  must  be  bent  in  the  shape  of  an  S  to 
raise  the  specimen  chamber  to  a  point  where  the  outlet  is  above  the  lowest 
part  of  the  mixing  chamber  to  keep  the  apparatus  from  running  dry.  The 
same  result  can  of  course  be  obtained  by  inserting  the  specimen  chamber 
under  the  mixing  chamber  and  bending  up  the  outlet  tube  to  a  point  above 
the  top  of  the  specimen  chamber. 

This  apparatus  was  for  this  work  preferred  to  the  Cobb  type  because 
it  permitted  the  dehydration  of  a  large  amount  of  material  at  one  time  and 
so  saved  an  infinite  amount  of  labor. 

When  the  specimens  were  dehydrated  they  were  removed  from  the 
chamber  into  a  small  stendor  dish  and  cleared  in  xylene  by  means  of  the 
string  differentiator  described  by  Magath.  This  consists  essentially  of 
three  dishes  placed  one  above  the  other  like  steps  in  a  stairway.  The  upper 
dish  contains  the  liquid  to  be  introduced,  the  middle  dish  contains  the 
specimens,  and  the  lower  one  the  waste.  The  liquid  is  transferred  from 
dish  to  dish  by  means  of  string  siphons.  The  string  drawing  the  liquid 
from  the  specimen  dish  does  not  reach  the  bottom  of  that  dish  and  so 
prevents  the  removal  of  all  the  liquid  from-  the  specimens  when  the  upper 
dish  goes  dry.  The  whole  apparatus  is  covered  by  a  bell  jar  sealed  at  the 
bottom  to  prevent  the  alcohol  from  absorbing  moisture  from  the  air. 

This  differentiator  was  later  adapted  also  for  dehydrations.  The  chief 
objection  to  the  use  of  the  apparatus  described  by  Magath  for  dehydration 
lies  in  the  fact  that  the  stronger  alcohol  introduced  into  the  specimen  dish 
tends  to  form  a  layer  at  the  top  and  is  drawn  off  again  by  the  second  string, 
increasing  only  very  slowly  the  strength  of  the  lower  alcohol,  causing  an 
enormous  waste  of  liquid,  and  usually  ruining  the  specimens.  It  is  possible 
to  withdraw  the  alcohol  from  the  bottom  of  the  specimen  dish  by  means  of 
a  capillary  glass  tube  bent  in  the  shape  of  a  U.  This  capillary  tube  must 
widen  out  rather  suddenly  at  the  outlet  to  an  inside  diameter  of  about  two 
millimeters  and  this  end  must  be  bent  outward  so  that  the  liquid  drops 
freely  from  the  tube  without  touching  the  dish.  If  this  tube  is  not  widened 
at  the  outlet  it  is  impossible  to  keep  the  alcohol  in  the  specimen  dish  at 
the  proper  level  on  account  of  the  different  effect  of  capillarity  on  the 
different  grades  of  alcohol.  An  ordinary  capillary  tube  that  will  keep  water 
at  the  proper  level  will  drain  the  dish  completely  when  the  higher  grades 
of  alcohol  are  used.  The  level  at  which  the  liquid  will  be  maintained  is 
determined  by  the  position  of  the  outlet  of  the  capillary  tube  as  the  liquid 
will  stop  flowing  when  the  level  tends  to  become  lower  and  will  start 
automatically  when  that  level  is  raised.  For  clearing  specimens  dehyd- 
rated in  this  differentiator  the  capillary  tube  is  replaced  by  a  string. 
This  apparatus  is  by  far  the  most  convenient  and  the  safest  for  delicate 
specimens  as  they  can  be  kept  in  the  same  dish  thruout  the  entire  process 
of  dehydration  and  infiltration. 


14  ILUNOIS  BIOLOGICAL  MONOGRAPHS  (134 

Specimens  transferred  from  xylene  to  a  solution  of  paraffin  in  xylene  or 
from  a  saturated  solution  of  paraffin  in  xylene  to  melted  paraffin  are 
usually  injured  by  the  appearance  of  gas  bubbles  in  the  tissues  and  conse- 
quent tearing  and  distortion.  To  avoid  this  the  following  method  of  infil- 
tration was  introduced.  Pieces  of  solid  paraffin  are  successively  added  to 
the  xylene  containing  the  specimens  until  the  solution  becomes  saturated. 
When  the  solution  is  saturated  at  room  temperature  the  dish  is  placed  in 
a  warming  oven  or  on  the  top  of  the  paraffin  bath  and  the  process  con- 
tinued till  saturation  is  again  reached.  The  infiltration  to  this  point  usually 
requires  two  to  three  days.  The  dish  is  now  placed  in  the  paraffin  bath 
and  the  process  continued  rather  rapidly  until  the  solution  becomes  practi- 
cally pure  paraffin.  The  specimens  are  then  transferred  to  pure  paraffin 
and  imbedded  after  about  two  hours.  The  entire  period  during  which  the 
specimens  are  left  in  the  paraffin  bath  is  usually  not  more  than  four  hours. 

For  imbedding  Gruebler's  best  paraffin  with  a  melting  point  of  56  to 
58"  C.  was  found  to  give  the  best  results.  The  ordinary  paraffins  were 
found  to  be  either  too  soft  or  too  brittle  for  this  work.  Parowax,  the 
Standard  Oil  product  on  sale  at  nearly  all  groceries,  would  be  an  excellent 
medium  if  the  temperature  of  the  sectioning  room  could  be  kept  down  to 
about  15°  C.  I 

For  sectioning  specimens  imbedded  in  the  hard  paraffin  at  ordinary 
room  temperature  it  was  necessary  to  dip  the  trimmed  block  into  melted 
soft  paraffin.  After  cooling  the  soft  paraffin  was  removed  from  all  sides 
except  the  lower.  Blocks  treated  in  that  way,  when  sectioned  7  to  lO/x  thick, 
produce  beautiful  ribbons  in  which  the  sections  show  no  evident  shrinkage 
or  rolling. 

All  cross  sections  and  most  of  the  longitudinal  sections  were  cut  7ju  thick. 
Longitudinal  sections  of  specimens  in  which  the  adult  cuticula  had  been 
formed  had  to  be  cut  10)u  and  even  then  gave  only  poor  results  on  account  of 
the  unequal  expansion  and  contraction  of  different  parts  when  the  sections 
were  cut.  Cross  sections  of  such  specimens  also  showed  distortions  from 
the  same  causes.  In  younger  specimens  in  which  the  cuticula  was  still  soft 
the  sections  could  be  flattened  out  fairly  well  by  placing  them  on  water  on 
a  slide  and  warming  the  slide  suddenly  to  the  point  where  the  paraffin 
began  to  become  clear  but  did  not  become  completely  melted.  Even  with 
that  treatment  the  cuticula  often  retained  a  wavy  outline  not  normal  to 
the  living  specimen.  For  later  stages  the  warming  usually  had  to  be  con- 
tinued until  the  paraffin  was  completely  melted.  Good  results  were 
obtained  with  such  specimens  when  the  slide  was  placed  in  the  paraffin 
bath  for  half  an  hour  or  more  until  the  water  had  evaporated  from  under 
the  ribbons.  For  that  purpose  the  bath  must  be  warm  enough  to  melt 
the  paraffin  as  otherwise  blistering  takes  place  and  the  sections  may  be 
ruined. 


135]  UFE  HISTORY  OP  GORDIUS  AND  PARAGORDIUS— MAY  15 

In  all  cases  the  sections  were  fixed  to  the  slide  by  means  of  Meyer's 
albumen  fixative.  Slides  containing  older  specimens  had  further  to  be 
treated  with  a  very  thin  solution  of  celloiden  while  transferring  from  abso- 
lute alcohol  to  95%  before  staining. 

In  sectioning  adults  the  friction  between  the  specimen  and  the  knife 
often  caused  the  ribbon  to  become  highly  charged  with  static  electricity. 
This  was  especially  true  of  specimens  that  had  become  excessively  hardened 
in  the  process  of  dehydration  and  infiltration.  The  only  remedy  was  to 
trim  the  block  less  closely  and  make  sure  that  it  was  properly  treated  with 
soft  parafl&n.  The  same  rules  had  to  be  followed  in  sectioning  crickets 
and  grasshoppers. 

The  best  stain  was  found  to  be  iron  hematoxylin.  Unna's  polychro- 
matic methylene  blue  method  with  orcein  as  a  counter  stain  gave  fair 
results,  Mallory's  connective  tissue  stain  was  useful  for  demonstrating 
basement  membranes;  Delafield's  hematoxylin,  Ehrlich's  hematoxylin  and 
the  carmine  stains  gave  very  mediocre  results. 

The  iron  hematoxylin  method  had  to  be  modified  according  to  the 
developmental  stage  and  condition  of  the  material,  and  the  structures  to 
be  shown.  For  mordanting  a  4%  solution  of  iron  ammonia  alum  was 
used  and  for  staining  a  0.5%  solution  of  hematoxylin  in  water.  Sections 
were  usually  mordanted  about  twice  as  long  as  they  were  stained  except  in 
case  of  very  short  staining  periods  when  they  were  mordanted  about  half 
an  hour. 

Older  parasitic  stages  were  usually  stained  from  half  an  hour  to  one 
hour,  adults  from  one  to  two  hours  or  for  nerve  structures  from  six  to 
twelve  hours,  younger  stages  for  very  short  periods,  sometimes  not  more 
than  thirty  seconds.  Destaining  was  nearly  always  done  in  a  saturated 
solution  of  picric  acid  in  water.  This  was  found  to  take  the  stain  out  more 
uniformly  than  did  the  iron  alum. 

For  counterstaining  the  slides  were  left  for  from  twelve  to  twenty-four 
hours  in  xylene  to  every  fifty  cubic  centimeters  of  which  had  been  added 
three  to  five  drops  of  a  saturated  solution  of  eosin  in  absolute  alcohol. 
Fresh  eosin  must  be  added  from  time  to  time  as  it  precipitate  very  rapidly 
unless  there  is  a  large  amount  of  alcohol  in  the  xylene. 


16  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [136 


OBSERVATIONS  ON  GORDIUS  ROBUSTUS 

Since  the  investigation  was  begun  on  Gordius  robustus  Leidy  and  since 
the  series  of  observations  is  most  complete  in  this  species,  it  is  but  natural 
that  it  should  form  the  first  part  of  the  discussion. 

DETERMINATION  OF  SPECIES 

On  account  of  the  confusion  existing  in  the  literature  in  regard  to  this 
and  related  species  it  is  necessary  to  take  up  at  this  point  a  precise  char- 
acterization of  the  species  and  a  determination  of  its  position  in  the  group. 
The  species  was  named  by  Leidy  in  1851  and  specimens  were  again  referred 
to  it  in  1879.  The  single  female  of  1851  has  not  been  preserved  but  the 
specimens  of  1879  have  fortunately  been  kept  in  fair  condition.  Leidy 's 
early  characterizations  are  not  sufficient  for  identification  but  his  descrip- 
tion of  1879  is  fairly  complete  and  the  material  is  available  for  study. 
Montgomery  has  given  a  somewhat  detailed  description  of  the  species,  but 
he  overlooked  one  of  the  most  essential  characters,  the  dorsal  and  ventral 
bands.  Only  a  general  description  of  the  species  will  be  given  at  this 
point,  details  of  the  structure  being  left  for  the  discussion  of  the  adult 
morphology. 

Dimensions.  Of  the  specimens  collected  near  Urbana  the  females  vary 
in  length  from  100  to  470  mm.  and  the  males  from  120  to  420  mm.  The 
diameter  of  the  females  ranges  from  0.5  to  1.25  mm.,  that  of  the  males 
from  0.3  to  0.75  mm.  Some  of  Montgomery's  specimens  from  California 
are  considerably  larger.  The  females  in  Leidy's  collection  are  very  short 
and  thick. 

Form.  Both  males  and  females  are  cylindrical,  decreasing  very  slightly 
in  diameter  toward  the  ends,  the  females  more  than  the  males.  The  shape 
of  the  anterior  end  is  essentially  the  same  in  both  sexes.  In  the  average 
specimen  the  end  is  rounded  in  the  shape  of  a  hemisphere,  separated  from 
the  body  by  a  very  slight  constriction  and  of  the  same  diameter  as  the  body 
just  behind  the  constriction  (Fig.  27).  In  very  stout-bodied  females  there 
is  no  trace  of  a  constriction  and  the  body  becomes  distinctly  attenuated 
just  before  the  end.  This  condition  is  at  its  extreme  in  case  of  the  short, 
thick  females  in  Leidy's  collection  (Fig.  28). 

The  posterior  extremity  of  the  female  is  slightly  enlarged  in  the  shape 
of  a  bulb  and  abruptly  truncated  at  the  end  (Figs.  25,  26).  The  cloacal 
aperture  is  located  at  the  center  of  the  truncated  area  and  there  is  no 
trace  of  a  dorso- ventral  furrow  (Fig.  34). 


137]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  17 

The  posterior  end  of  the  male  bears  two  short,  stout  prongs  (Figs.  8, 32). 
The  length  of  the  prongs  varies  somewhat,  but  is  usually  not  much  more 
than  half  the  diameter  of  the  body.  Each  prong  is  jdi  conical  shape  with 
a  slight  flattening  on  the  inner  side.  The  body  attenuates  rapidly  dorso- 
ventrally  at  the  base  of  the  prongs  so  that  the  diameter  of  the  latter  is  less 
than  half  that  of  the  body  (Fig.  24).  On  the  ventral  side,  a  short  distance 
anterior  to  the  bifurcation  is  a  crescent-shaped  ridge  with  the  ends  of  the 
crescent  passing  slightly  onto  the  bases  of  the  prongs.  I  have  usually 
found  this  ridge  to  be  a  broad,  open  crescent  and  not  U  or  V-shaped  as 
represented  in  most  of  Montgomery's  figures.  The  anus  is  located  a  short 
distance  anterior  to  the  middle  of  the  crescent,  almost  at  its  very  base. 

Color.  The  usual  color  is  light  brown,  but  specimens  vary  from  nearly 
white  to  nearly  black  and  females  that  have  deposited  their  eggs  are  gray. 
When  light  is  reflected  in  the  proper  way  the  cuticula  shows  a  distinct 
iridescence,  very  pronounced  in  females  after  deposition  of  the  eggs.  Such 
females  examined  in  the  sunlight  present  brilliantly  all  the  colors  of  the 
rainbow.  Ordinarily  the  iridescence  gives  the  body  of  the  worm  the  appear- 
ance of  being  longitudinally  corrugated.  The  anterior  end  is  clear  white 
followed  by  a  ring  of  dark  brown  which  passes  rather  abruptly  into  the 
normal  brown  of  the  body.  At  the  center  of  the  anterior  white  area  is 
often  found  a  black  spot  indicating  the  position  of  the  mouth  (Fig.  33). 
Passing  backward  from  the  dark  ring  are  two  bands,  one  ventral  and  one 
dorsal,  slightly  darker  than  the  rest  of  the  body  (Figs.  26, 27,  28).  These 
bands  can  usually  be  traced  to  the  posterior  end  of  the  female,  but  are  more 
difficult  to  trace  in  the  male.  Even  there  the  dorsal  line  can  often  be  traced 
to  the  base  of  the  fork  while  the  ventral  line  disappears  a  short  distance 
before  the  anus.  Montgomery  does  not  mention  these  lines  or  bands  in 
his  description  of  the  species,  but  I  have  found  them  present  in  all  of  his 
material  that  I  have  examined  as  well  as  in  Leidy's  material.  They  are 
mentioned  by  Leidy  in  his  description  of  1879.  In  the  female  the  cloacal 
opening  is  situated  at  the  center  of  a  dark  area,  which  itself  is  surrounded 
by  an  area  slightly  lighter  than  the  body  color,  and  around  that  is  a  brown 
circle,  the  dark  color  of  which  passes  more  or  less  gradually  into  the  general 
body  color  (Fig.  34).  In  the  male  the  crescent  is  dark  brown,  almost  black, 
and  there  is  a  small  dark  area  surrounding  the  anus  (Fig.  32).  Lighter 
spots  scattered  over  the  body  may  or  may  not  be  present.  I  have  found 
them  on  many  specimens  at  Urbana  (Fig.  16),  but  never  as  pronounced  as 
in  Montgomery's  specimens  from  California. 

Cuticula.  The  cuticula  never  shows  any  traces  of  areoles.  Under  low 
magnification  it  appears  to  be  divided  into  rhomboidal  areas,  while  higher 
magnification  shows  a  system  of  finer  intersecting  lines  (Figs.  4,  5).  The 
white  area  at  the  anterior  end  is  of  more  homogeneous  structure.  Bristles 
or  hairs  are  present  over  the  entire  body.    Montgomery  says   they  are 


18  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [138 

branching,  but  I  have  been  unable  to  find  any  branching  forms  and,  from 
the  manner  in  which  they  develop,  I  do  not  beheve  that  branching  forms 
occur  in  this  species.  The  branching  forms  probably  occur  on  some  other 
species  that  Montgomery  regarded  as  identical  with  this.  The  bristles  are 
more  abundant  at  the  two  ends.  In  the  males  on  the  outside  of  the  prongs 
they  are  slightly  longer  than  elsewhere  and  usually  curved,  while  on  the 
inner  surfaces  there  are  very  short,  conical  setae  (Figs.  121, 122, 123).  No 
special  bristles  are  located  around  the  anus  of  the  male  (Figs.  96,  97,  98). 

Eggs  and  larvae.  In  nature  the  eggs  are  laid  in  thick  cords  which  break 
up  into  pieces  seldom  more  than  10  to  15  mm.  long  and  of  a  diameter 
nearly  equal  to  that  of  the  worm.  The  larva  belongs  to  the  type  with  a 
single  terminal  spine  at  the  posterior  end.  In  the  newly  hatched  larva 
(Fig.  20)  the  body  is  about  twice  as  long  as  the  proboscis  but  later  becomes 
much  reduced  (Fig.  14). 

Montgomery  at  first  referred  this  species  to  Gordius  aquaiicus  var. 
robustus.  Later  he  regarded  it  as  Gordius  villoti  and  eliminated  the  variety. 
It  belongs  to  the  group  known  by  most  European  writers  as  Gordius  aquati- 
cus.  The  identification  is  usually  based  on  Villot's  description  of  what  he 
regarded  to  be  Dujardin's  Gordius  aquaticus.  Rosa  regarded  the  identity 
of  the  two  species  as  impossible  or  at  least  highly  improbable  and  called  Vil- 
lot's species  Gordius  villoti.  At  the  same  time  he  redescribed  the  species, 
basing  his  description  on  a  male  and  two  females.  He  found  on  the  surface 
irregularly  polygonal  areolae  which  it  is  difficult  to  interpret  as  the  rhom- 
boidal  areas  in  the  cuticula.  ViUot  later  called  them  pseudoareolae  and  he 
as  well  as  Camerano  included  them  in  the  description  of  Gordius  aquati- 
cus, stating  that  they  are  not  present  in  all  specimens.  Of  Rosa's  specimens 
only  the  male  possessed  the  dorsal  and  ventral  bands  and  the  character  is 
not  included  in  the  original  description  of  Villot's  species.  It  is  however 
mentioned  in  the  description  of  Dujardin  and  Villot's  later  descriptions. 
I  have  never  found  the  bands  absent  on  any  specimen  of  Gordius  robustus 
or  Paragordius  varius  and  believe  the  character  is  not  variable  within  a 
species.  On  account  of  this  and  other  differences  between  the  male  and 
females  described  by  Rosa  it  seems  certain  that  he  included  at  least  two 
species  in  his  description,  and  it  is  possible  that  neither  of  them  was  identi- 
cal with  Villot's  species. 

Rosa  believes  that  Villot's  species  can  not  be  identical  with  that  of 
Dujardin  because  Dujardin's  description  mentions  pores  0.006mm.  in 
diameter  in  the  fibrous  cuticula  which  VOlot  does  not  mention.  On  the 
other  hand  Villot  mentions  a  dark  collar  behind  the  white  anterior  end,  a 
postcloacal  crescent  in  the  male  and  clear  spots  in  the  cuticula  not  mention- 
ed by  Dujardin.  Villot  in  1886,  however,  does  describe  pores  in  the  ^rous 
cuticula  which  he  claims  may  attain  the  diameter  of  0.006mm.  On  the 
other  hand  Dujardin  describes  clear  areas  0.06mm.  in  diameter  which  he 


139]  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  19 

regarded  as  openings  in  the  homogeneous  cuticula.  Furthermore,  since 
the  dark  collar  is  almost  universally  present  in  Gordiacea  of  this  group,  it 
is  probable  that  it  was  not  actually  lacking  in  the  specimen  of  Dujardin; 
and  the  fact  that  he  overlooked  this  leads  also  to  the  possibility  that  he 
overlooked  a  crescent  that  may  have  been  present.  The  latter  assumption 
is  moreover  justified  because  there  is  at  present  no  form  known  with  a  cuti- 
cula that  is  devoid  of  true  areoles  and  in  which  the  male  possesses  no 
crescent.  Indeed  Camerano  makes  the  combination  of  presence  of  crescent 
and  absence  of  areoles  a  generic  character.  The  use  of  the  name  Gordius 
aquaticus  by  Villot  seems  justified  in  the  light  of  these  considerations. 
But  his  description  probably  includes  a  group  of  closely  related  species 
which  some  future  investigator  in  Europe  may  be  able  to  separate. 

Since  there  are  several  characters  ascribed  by  various  authors  to  the 
European  species  that  are  not  present  in  Gordius  robustus  the  two  species 
can  not  be  combined.  Among  the  characters  not  present  in  Gordius  robustus 
are  pseudoareolae,  pores  in  the  cuticula,  a  dorsoventral  furrow  at  the  pos- 
terior end  of  the  female,  and  groups  of  cells  extending  from  the  hypoderm 
into  the  cuticula  as  described  by  Camerano  (1888)  and  Rauther  (1905). 
The  larva,  also,  of  the  European  form  appears  to  have  a  shorter  body  than 
that  of  the  American  species. 

It  is  difl&cult  to  see  why  Montgomery  assigned  the  American  species 
to  Gordius  villoti,  since  he  himself  states  that  Leidy's  descriptions  are 
sufficient  to  establish  the  identity  of  the  species  and  he  had  Leidy's  material 
at  hand  for  additional  information  if  necessary;  furthermore,  he  certainly 
was  aware  of  the  fact  that  Leidy's  first  description  was  given  in  1851  and 
his  second  description  in  1879,  while  that  of  Rosa  did  not  appear  until  1882. 

HABITS  OF  ADULTS 

Gordius  robustus  emerges  from  its  host  during  September  and  October 
and  possibly  the  latter  part  of  August.  Specimens  may  then  be  found 
swimming  freely  in  the  streams  or  stranded  at  the  water's  edge.  It  is  at 
this  time  that  they  are  most  easily  obtained  in  general  collections.  But 
the  period  of  migration  does  not  last  very  long  as  the  specimens  soon  be- 
come entangled  in  the  grass  and  debris  along  the  edge  of  the  water. 

During  November  and  December  I  have  still  succeeded  in  finding 
specimens  in  the  grass  just  below  the  level  of  the  water  in  small  brooks. 
Even  at  this  time  they  tend  to  accumulate  at  or  just  below  rapids.  During 
January  and  February  I  have  made  no  collections,  but  the  latter  part  of 
March,  when  the  ice  has  gone,  specimens  are  again  found  in  the  grass.  At 
that  time  I  have  usually  found  them  deeper  down,  entangled  in  the  roots 
of  the  grass  even  several  inches  in  the  ground. 

During  April  and  early  May  there  seems  to  be  another  migration  on 
the  part  of  some  of  the  worms,  but  I  have  never  found  them  free  in  the 
water.    Since  worms  in  captivity  will  usually  remain  quiet  during  the  day 


20  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [140 

but  become  active  during  the  early  part  of  the  night  it  is  probable  that 
migrations  in  the  streams  occur  at  that  time.  By  the  middle  of  May  all  the 
worms  seem  to  have  accumulated  among  the  roots  of  grass  in  or  at  the 
edges  of  rapids. 

It  is  likely  that  copulation  does  not  ordinarily  take  place  during  the 
fall  migration,  as  specimens  at  that  time  are  usually  found  isolated  and  seem 
to  remain  more  or  less  isolated  during  the  winter.  During  the  spring 
migration,  however,  they  gather  together  in  large  numbers  and  I  have 
several  times  found  females  that  still  retained  the  mass  of  spermatozoa  at 
the  posterior  end,  showing  that  copulation  had  taken  place  not  more  than 
three  days  before.    It  is  soon  after  this  migration  that  egg-laying  begins. 

The  process  of  copulation  is  not  difl&cult  to  observe.  If  two  fresh  worms, 
male  and  female,  are  placed  in  a  glass  cylinder  about  10  cm.  in  diameter, 
filled  with  water,  copulation  takes  place  in  a  short  time  and  may  be 
observed  thru  the  walls  of  the  cylinder.  When  specimens  are  placed  in  a 
large  open  dish  they  swim  about  actively  for  a  long  time  and  copulation 
usually  does  not  take  place  until  the  latter  part  of  the  night,  when  they 
become  more  quiet,  and  sometimes  not  until  the  second  night.  For  the 
observations  for  this  report  I  used  specimens  that  had  just  emerged  from 
their  hosts,  but  in  early  spring  collections  most  of  the  females  copulate 
after  being  brought  to  the  laboratory  and  observations  could  easUy  be 
made  on  them.  In  spite  of  the  fact  that  egg-laying  does  not  seem  to  take 
place  in  the  fall,  the  specimens  are  mature  for  copulation  when  they  emerge. 
I  have  kept  males  and  females  that  had  just  emerged  or  had  been  removed 
from  the  hosts  in  open  dishes  and  had  copulation  take  place  within  48 
hours  after  emergence. 

There  seems  to  be  no  definitely  directed  effort  on  the  part  of  either  male 
or  female  to  seek  its  mate.  There  is  of  course  the  usual  tendency  on  the 
part  of  both  to  become  entangled  with  the  other,  but  the  solid  knot  that 
makes  observation  impossible  is  usually  not  formed  by  two  specimens 
until  they  have  been  together  for  a  long  time.  The  two  worms  merely 
become  intertwined  at  places  and  then  again  disentangled,  only  to  become 
reentangled  again.  That  process  is  continued  until  finally  the  body  of  the 
female  comes  to  lie  within  the  spiral  coil  formed  by  the  posterior  end  of  the 
male.  This  coil  soon  tightens,  the  prongs  are  spread  over  the  body  of  the 
female  (Fig.  30),  and  the  posterior  end  of  the  male  with  a  rotary  motion 
passes  backward  over  the  body  of  the  female.  The  male  does  not  seem  to 
choose  the  direction  in  which  it  is  to  move  except  that  it  tends  to  move 
contrary  to  the  motion  of  the  female.  The  direction  taken  is  nearly  as 
frequently  toward  the  anterior  end  of  the  female  as  toward  the  posterior 
end.  Usually  after  several  trials  the  posterior  end  of  the  male  passes  over 
the  posterior  end  of  the  female.  When  the  prongs  have  already  passed 
over  the  end  (Fig.  31)  a  discharge  of  sperm  takes  place.    The  cloacal  open- 


141]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  21 

ings  of  the  two  specimens  are  not  superimposed  at  this  time  and  the  sperm 
mass  does  not  enter  the  body  of  the  female  but  adheres  to  the  outside. 
The  discharge  usually  lasts  not  more  than  thirty  seconds  and  during  this 
time  the  male  continues  to  rotate  on  the  body  of  the  female.  The  sperm 
seems  to  be  fluid  when  it  leaves  the  body  of  the  male  but  soon  solidifies. 
Some  is  lost  in  the  water. 

The  sperm  mass  (Figs.  10,  113)  disappears  from  the  female  within  two 
or  three  days.  Most  of  the  spermatozoa  pass  into  the  seminal  receptacle. 
The  mass  is  so  tough  that  it  is  almost  impossible  to  crush  it  in  order 
to  make  a  microscopic  preparation  and  it  does  not  seem  possible 
that  many  spermatozoa  are  brushed  off.  The  migration  into  the  seminal 
receptacle  is  probably  passive,  as  the  spermatozoa  show  no  movement 
when  placed  on  a  slide. 

The  first  eggs  appear  the  latter  part  of  April  and  laying  continues  until 
early  June.  The  eggs  are  deposited  while  the  worms  remain  entangled  in 
masses  among  the  roots  of  grass.  They  are  laid  in  thick  cords  about  0.5mm. 
in  diameter  and  break  up  into  short  pieces  from  5  to  30mm.  long.  When 
fresh  they  are  pure  white,  but  soon  become  discolored  by  the  surrounding 
earth.  They  do  not  adhere  very  strongly  to  each  other  and  are  easily  crush- 
ed under  a  cover  glass  for  microscopic  examination. 

After  the  deposition  of  the  eggs  the  adults  soon  become  inactive  and 
begin  to  die  and  disintegrate  in  parts.  One  may  actually  find  females 
with  the  anterior  end  dead  and  disintegrated  so  that  nothing  but  the  cuti- 
cula  is  left  while  the  posterior  end  is  still  depositing  eggs.  More  commonly, 
however,  disintegration  does  not  appear  until  all  the  reproductive  products 
have  been  discharged  and  it  may  begin  at  any  part  of  the  body  or  the  whole 
specimen  may  die  at  once.  Males  usually  die  a  week  or  two  earlier  than  do 
the  females.    Most  of  the  specimens  are  dead  by  the  middle  of  June. 

EARLY  DEVELOPMENT 

Since  Montgomery  in  1904  gave  a  detailed  account  of  the  development 
of  the  larva  of  Paragordius  varius  it  seemed  only  of  minor  importance  to 
repeat  his  work  on  some  other  species  and  consequently  little  attention 
was  at  first  given  to  the  embryology  of  this  species.  The  observations 
that  were  made,  however,  show  that  not  only  the  larval  development  of 
Gordius  robustus  but  also  that  of  Paragordius  varius  requires  further  inves- 
tigation. It  has  not  been  possible  to  undertake  that  investigation  for  the 
present  report. 

To  fill  out  the  gap  I  shall  give  a  very  general  account  of  the  larval 
development  of  Paragordius  varius  as  described  by  Montgomery,  The 
eggs  are  fertilized  in  the  cloaca  and  the  two  polar  bodies  are  given  off  soon 
afterwards.  The  cleavage  is  total  and  adequal  and  soon  forms  a  coelo- 
blastula  which  early  passes  over  into  a  typical  gastrula.  Mesenchyme  is 
formed  by  the  separation  of  cells  from  the  invaginated  entoderm.    At  the 


22  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [142 

end  opposite  the  blastopore  the  ectoderm  thickens  and  forms  a  second 
invagination,  that  of  the  proboscis.  The  entire  proboscis  develops  from 
ectoderm  except  for  a  few  mesenchyme  cells  which  have  migrated  into  it 
to  form  the  muscles.  The  blastopore  becomes  nearly  closed  and  the  an- 
terior end  of  the  intestine  does  not  communicate  with  the  cavity  of  the 
proboscis  during  the  embryological  stages. 

The  description  of  the  larva  also  can  be  given  only  in  the  most  general 
terms  at  this  time.  The  larva  of  Gordius  robustus  dilffers  greatly  in  form 
from  that  of  Paragordius  varius,  but  in  essential  structures  the  two  do  not 
seem  to  differ  much.  The  newly  hatched  larva  (Fig.  20)  is  very  much 
elongated,  but  after  a  week  or  so  it  has  become  shrunken  to  about  half  its 
original  length  (Fig.  14)  and  has  increased  slightly  in  diameter.  Like  all 
other  known  Gordius  larvae  it  consists  of  proboscis  and  body.  The  pro- 
boscis is  armed  in  front  with  three  retractile  stylets  and  at  the  sides  with 
three  circles  of  hooks  which  point  backward  when  the  proboscis  is  extended, 
but  are  withdrawn  into  the  proboscis  when  this  is  retracted.  A  set  of  retrac- 
tor muscles  is  inserted  at  the  base  of  the  stylets  and  protractors  lie  close 
to  the  outer  wall  of  the  proboscis.  The  body  in  the  newly  hatched  larva 
is  at  least  twice  as  long  as  the  proboscis  and  of  a  slightly  smaller  diameter. 
Both  body  and  proboscis  are  covered  by  external,  more  or  less  irregular 
cuticular  rings  which  do  not  seem  to  be  in  any  way  related  to  the  deeper 
structures  of  the  larva.  The  posterior  end  of  the  body  runs  out  to  a  point 
resembling  a  heavy  spine.  Between  the  proboscis  and  the  body  there 
appears  to  lie  a  partition  separating  the  end  of  the  intestine  on  one  side  from 
a  cord  of  cells  coming  from  the  base  of  the  stylets  on  the  other.  Just  behind 
this  partition  is  a  mass  of  cells  belonging  to  the  intestine  which  farther 
back  has  very  thin  walls  and  encloses  within  its  lumen  two  elongated  masses 
of  a  homogeneous,  highly  refractive  substance.  Montgomery  figures 
similar  masses  in  the  intestine  of  Paragordius  varius  and  regards  them  as 
excretory  waste.  In  Gordius  robustus  these  masses  are  later  absorbed  as 
large  cells  invade  this  region.  The  intestine  opens  at  the  posterior  end  on 
the  ventral  side  somewhat  anterior  to  the  spinelike  elongation. 

Beginning  near  the  proboscis  and  extending  backward  two-thirds  of  the 
length  of  the  body  on  the  ventral  side  are  two  rows  of  nuclei  indicating  the 
rudiments  of  the  ventral  nerve  cord.  Only  longitudinal  muscles  appear  to 
be  present  in  the  body  and  they  adhere  so  closely  to  the  outer  wall  that  it 
is  difl5cult  to  detect  them. 

When  fully  developed  the  larva  ruptures  the  egg-membrane  and  escapes 
from  the  egg-string  by  means  of  the  armature  of  its  proboscis.  Quite  active 
at  first,  it  becomes  more  and  more  sluggish  as  it  grows  older.  Larvae 
picked  up  with  a  pipette  from  the  bottom  of  the  dish  containing  the  eggs 
usually  show  only  a  few  active  forms.  If  among  a  number  of  larvae  in  an 
open  drop  on  a  slide  about  ten  per  cent  are  active,  then  when  a  coverglass 


143]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  23 

is  placed  over  the  drop  about  half  of  the  specimens  will  become  active 
within  five  or  ten  minutes.  The  reaction  is  not  due  to  pressure  as  the 
larvae  can  easily  stand  on  end  in  the  ordinary  film  of  water.  It  may  be  a 
reaction  to  the  lack  of  oxygen  or  the  presence  of  carbon  dioxide  in  the 
water. 

The  larvae  bore  their  way  into  any  animal  tissue  that  happens  to  be 
accessible  at  the  time.  Villot  was  the  first  to  discover  this,  and  since  he 
regarded  all  these  animals  as  true  hosts  of  the  parasite,  he  stated  that 
Gordius  has  no  specific  hosts.  Later  Villot  himself,  Montgomery  and 
others  found  that  the  larvae  merely  encyst  in  most  of  these  animals  and 
are  unable  to  undergo  further  development. 

PARASITISM 

With  the  entrance  of  the  larva  into  the  proper  host  begins  one  of  the 
most  important  phases  of  the  life  cycle,  the  period  that  leads  thru  growth 
and  differentiation  to  the  formation  of  the  mature  worm. 

The  final  and  perhaps  the  only  hosts  of  Gordius  robustus  I  have  found 
to  be  members  of  the  grasshopper  family  Locustidae.  The  most  common 
host  around  Urbana  is  Orchelimum  vulgare  Harris,  but  Orchelimum  nigripes 
Scudder  and  Xiphidium  nemorale  Scudder  seem  to  be  equally  heavily 
infected  tho  less  common,  and  I  have  obtained  two  adult  parasites  from  a 
female  of  Scudderia  furcata  Brunner.  Over  100  specimens  of  Xiphidium 
fasciatum  (DeGeer)  from  localities  in  which  Orchelimum  vulgare  was  heavily 
infected  were  examined  but  no  infection  was  found.  Over  200  specimens 
each  of  Melanoplus  diferentialis  and  Melanoplus  femur-ruhrum  from  similar 
localities  also  proved  to  be  not  infected.  Large  numbers  of  Gryllus  assi- 
milis  and  Nemobius  fasciatus  examined  in  the  investigation  on  Paragordius 
varius  were  also  not  infected  with  Gordius  robustus.  Many  aquatic  insect 
larvae  were  also  examined,  but  no  infected  specimens  were  found.  From 
two  to  three  percent  of  the  crickets  and  grasshoppers  examined  were  found 
to  be  infected  with  Mermithidae. 

An  intermediate  host  is  not  necessary.  If  one  occurs  in  nature  it  can 
be  nothing  more  than  a  carrier  in  which  the  larva  undergoes  no  change. 
Evidence  presented  later  shows  that  a  larva  that  has  begun  to  change  into 
the  parasitic  form  can  not  undergo  a  change  of  hosts  without  being  destroy- 
ed in  the  process.  Furthermore,  I  have  succeeded  in  producing  in  the 
laboratory  an  infection  of  at  least  fifty  per  cent  in  Locustidae  collected 
in  a  locality  in  which  later  collections  showed  that  no  infection  occurred 
in  nature. 

I  1.  On  July  6,  1916  forty-one  young  Locustidae,  mostly  Xiphidium 
fasciatum  and  Orchelimum  vulgare  were  infected  by  injecting  a  drop  of  water 
in  which  larvae  of  Gordius  robustus  were  suspended  into  the  abdomen  by 
means  of  a  capillary  pipette  made  of  hard  glass.  From  counts  made  on 
similar  drops  of  the  suspension  placed  on  a  slide  under  the  microscope  it 


24  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [144 

was  estiriiated  that  from  five  to  ten  larvae  were  injected  into  each  host. 
On  account  of  the  unfavorable  conditions  under  which  they  were  kept  most 
of  the  hosts  died  in  the  next  few  days.  On  the  ninth,  six  of  the  infected 
hosts  were  killed,  the  tissues  teased  out  in  salt  solution  and  the  sediment 
examined.  Two  active  larvae  of  Gordius  robustus  were  found,  both  show- 
ing signs  of  having  begun  their  development.  Both  were  lost  in  an  attempt 
to  stain  and  mount  them.  On  July  11  all  hosts  were  dead  except  five. 
When  these  were  examined  as  before,  four  somewhat  older,  but  still  active 
larvae  were  found.    They  also  were  lost  by  accident. 

I  2.  Suspensions  of  larvae  of  Gordius  robustus  were  injected  into  the 
mouths  of  eleven  young  Locustidae  on  July  6.    All  died  within  a  few  days. 

I  4.  Four  young  specimens  of  Orchelimum  vulgare  were  infected  as 
in  1 1  on  July  9.  On  July  15  three  of  the  specimens  were  examined  and  all 
were  found  to  be  infected,  yielding  four  small  parasites  (Figs.  9, 11).  The 
other  host  died. 

I  7.  On  July  11  fifty- three  Locustidae  mostly  by  Or cAe/i www  fw/^are, 
which  had  become  easily  recognizable  by  this  time,  were  infected  as  before. 
Specimens  of  this  lot  were  killed  for  sectioning,  at  first  every  day  and  later 
every  two  days.  On  July  15  an  adult  was  examined  but  nothing  found. 
Another  adult  was  killed  and  examined  on  July  22  and  found  to  contain 
three  young  worms,  the  longest  being  about  10mm.  in  length  and  the 
smallest  one  about  5mm.  On  the  following  day  the  last  three  hosts  were 
examined  and  all  were  found  to  be  infected,  yielding  11  parasites  ranging 
from  3  to  10mm.  in  length. 

I  8.  On  July  14  seventy-eight  Locustidae,  mostly  young  Orchelimum 
vulgare  were  infected.  Some  of  these  were  again  killed  for  sectioning  and 
staining  as  were  those  of  I  7.  One  adult  host  was  examined  on  July  22  and 
found  to  be  infected  with  one  young  parasite  (Fig.  15).  An  examination  of 
ten  more  hosts  on  the  following  day  yielded  only  a  single  parasite  about 
2mm.  long  in  the  coUed  stage.  On  August  11  the  last  two  specimens  were 
examined.  Only  one  was  infected  and  contained  two  parasites  25  and 
30mm.  long  respectively. 

Later  infection  experiments  proved  less  successful.  Of  45  control  hosts 
not  one  was  found  to  be  infected. 

Of  the  specimens  preserved  for  sectioning  only  seven  from  I  7  have 
been  thoroughly  examined  and  six  were  found  to  be  infected.  Sections  of 
some  of  the  specimens  found  are  shown  in  figures  47-49  and  50-55. 

The  results  of  these  infection  experiments  show  conclusively  that  an 
intermediate  host  is  not  necessary  for  Gordius  robustus. 

Infection  in  nature  must  begin  in  late  June  or  early  July  and  end  the 
latter  part  of  July  or  in  August.  The  young  of  Orchelimum  vulgare  collected 
early  in  July  were  still  small  and  could  not  have  hatched  more  than  a  week 
or  so  before  they  were  collected.  By  the  middle  of  September  most  of  the 
parasites  are  well  along  in  their  development. 


145] 


LIFE  HISTORY  OF  GOKDIUS  AND  PARAGORDIUS—MAY 


25 


TABLE  I 

RESULTS  OF  INFECTING  Orchelimum  vulgar e  with  larvae 
OF  Gordius  robustus  in  the  laboratory 


Exp, 

Date 
in 
1916 

No. 

Inocu- 
lated 

Examined 

No. 

Fresh 

SUdes 

No. 

Inf. 

Par. 

Not 
Inf. 

No. 

Inf. 

Par. 

Not 
Inf. 

I    1 

Jy.  6 

41 

11 

? 

6 

? 

I   4 

9 

4 

3 

3 

4 

0 

I    7 

11 

53 

5 

4 

14 

1 

7 

6 

7 

1 

I   8 

14 

78 

13 

3 

4 

10 

no 

22 

16 

16 

0 

0 

16 

111 

23 

15 

9 

1 

1 

8 

Control 

45 

0 

0 

45 

Infection  takes  place  at  or  near  the  place  where  the  larvae  have  hatched. 
In  the  spring  of  1914  Gordius  was  very  abundant  in  all  of  the  streams  at 
which  collections  were  made.  Later  all  specimens  of  Orchelimum  vulgar e 
collected  near  these  streams  were  equally  and  heavily  infected.  During 
the  summer  of  1915  the  streams  were  continually  flooded  and,  judging 
from  the  scarcity  of  Gordius  in  the  fall  of  that  year  and  the  following  spring 
the  infection  must  have  been  very  light.  The  only  place  where  any  appre- 
ciable infection  can  have  taken  place  is  a  stream  north  of  the  city  which 
ordinarily  goes  dry  during  the  summer  months.  It  was  in  that  locality 
that  adult  worms  were  found  in  the  spring  of  1916  and  the  Locustidae  were 
found  to  be  heavily  infected  later  in  the  summer.  The  stream  west  of 
Champaign  which  had  supplied  the  major  part  of  the  material  in  1914  is 
bounded  by  narrow,  steep  banks  and  the  high  water  must  have  prevented 
the  grass  from  growing  in  the  bed  of  the  stream  as  usual.  This  stream  is 
also  becoming  more  and  more  polluted  with  sewage  and  other  refuse.  Of 
453  specimens  of  Orchelimum  vulgare  collected  along  the  bed  of  this  stream 
August  28  to  September  4,  1916,  only  six  specimens  or  1.5  per  cent  were 
found  to  be  infected.  I  had  not  succeeded  in  finding  any  specimens  of 
Gordius  in  the  stream  the  previous  spring.  Of  555  specimens  of  Locustidae 
collected  in  the  bed  of  the  stream  north  of  Urbana  along  the  distance  show- 
ing the  heaviest  infection  110  specimens  or  about  20  per  cent  were  infected 
and  yielded  164  parasites  while  in  the  other  collection  no  host  had  more 
than  one  parasite.  A  collection  of  143  hosts  along  the  same  stream,  but 
starting  where  the  previous  collection  had  left  off,  contained  8  infected 
specimens  or  6  per  cent  and  only  a  single  parasite  was  found  in  each  host. 


26  JLUNOIS  BIOLOGICAL  MONOGRAPHS  [146 

These  data  show  that  infection  is  local  to  a  high  degree  and  consequently 
that  infection  must  take  place  at  the  point  where  the  larvae  occur;  in  other 
words,  that  the  larvae  are  not  widely  distributed  by  an  intermediate 
carrier.  The  data  also  show  that  the  host  itself  does  not  ordinarily  migrate 
very  much  during  the  summer.  The  migration  of  the  average  host  seems 
to  be  limited  to  a  radius  of  about  half  a  mile,  perhaps  less. 

Just  how  the  larva  enters  the  host  I  have  not  been  able  to  discover.  In 
the  spring  of  1914  when  the  infection  was  so  heavy  I  had  not  yet  discovered 
the  host  and  in  the  two  succeeding  years  the  infection  was  ordinarily  so  low 
that  an  attempt  to  work  out  that  particular  phase  of  the  problem  by  obser- 
vation in  nature  would  have  been  a  waste  of  time. 

It  will  be  sufficient  here  to  give  a  brief  account  of  the  habits  of  the  hosts, 
leaving  the  discussion  of  the  possible  modes  of  infection  to  be  taken  up 
later.  Altho  the  species  of  Orchelimum  and  Xiphidium  found  to  be  the 
hosts  of  Gordius  robustus  are  the  common  meadow  Locustidae,  they  are 
much  more  abundant  in  the  tall  grass  near  the  water's  edge  than  elsewhere. 
Orchelimum  vulgare  and  Orchelimum  nigripes  are  found  most  abundant 
right  at  the  water's  edge  while  Xiphidium  nemorale  is  more  abundant  on 
the  taller  weeds  or  on  the  banks  of  the  streams. 

The  species  are  omnivorous  but  feed  chiefly  on  grass  and  weeds. 
Several  times  I  have  found  Orchelimum  vulgare  feeding  on  other  insects. 
In  captivity  all  of  the  species  are  cannibals,  feeding  on  each  other  even 
when  in  larger  cages.  The  collected  grasshoppers  had  to  be  brought  home 
in  tightly  stoppered  bottles  in  which  the  oxygen  supply  soon  became  so 
low  that  the  insects  became  quiescent,  and  even  then  they  often  injured 
each  other  severely  before  they  could  be  brought  to  the  laboratory  and 
examined. 

Tho  the  species  are  so  abundant  on  the  grass  near  the  border  I  have 
never  seen  them  deliberately  entering  the  water.  But  their  behavior  differs 
so  greatly  during  the  different  times  of  the  day  that  it  is  possible  for  them 
to  enter  the  water  regularly  at  some  time  during  the  night  or  early  morning 
but  never  do  so  during  the  time  at  which  my  collections  were  made.  The 
specimens  are  most  active  during  the  early  part  of  the  day,  especially  when 
the  sun  shines.  Since  all  specimens  were  collected  by  hand,  simply  by 
approaching  slowly  and  grasping  them  suddenly,  it  was  almost  impossible 
to  get  specimens  during  the  forenoon  or  early  afternoon  of  a  hot,  sunny  day. 
Altho  on  such  days  the  males  are  singing  everywhere,  they  become  aware 
of  the  approach  and  drop  to  the  ground  long  before  they  are  in  reach. 
Contrary  to  the  habits  of  the  Acrididae,  these  Locustidae  never  leap  from 
place  to  place  to  escape  an  enemy,  but  drop  down  almost  perpendicularly 
to  a  lower  level  in  the  grass  or  even  to  the  ground.  They  either  remain 
quiet  where  they  drop  or  run  along  for  some  distance  and  then  remain 
quiet  so  that  it  is  almost  impossible  to  find  them.    When  situated  on  the 


147]  LIFE  HISTORY  OF  GORDl US  AND  PARAGORDIUS—MA  Y  27 

grass  over  the  water  they  do  not  hesitate  in  the  least  to  drop  down  into  the 
water  and  are  in  no  haste  to  get  back  to  land.  On  cloudy  days  the  speci- 
mens often  remain  at  the  bottom  of  the  grass  and  can  not  be  obtained  at 
all,  but  on  bright  days,  when  it  is  just  cloudy  enough  for  the  sun  to  be  shaded, 
many  of  them  come  up  and  are  easily  obtained  because  they  are  less  active 
than  on  sunny  days.  I  have  been  able  to  obtain  them  most  easily  at  twi- 
light just  after  sunset.  At  that  time  they  come  out  on  the  grass  and  weeds 
and  do  not  easily  become  aware  of  approach,  and  even  when  disturbed 
they  often  merely  run  along  to  a  new  position  without  making  any  serious 
attempt  to  escape. 

The  larvae  at  first  penetrate  the  adipose  tissues  of  the  hosts,  making 
their  way  not  only  between  the  cells  but  also  thru  them  (Figs.  47,  54). 

In  later  stages  they  come  to  lie  free  in  the  body  cavity  of  the  host 
(Fig.  55).  There  is  usually  a  difference  in  the  location  in  the  host  between 
the  Mermithidae  and  Gordiacea.  While  the  Gordiacea  occupy  exclusively 
the  body  cavity,  the  Mermithidae  usually  penetrate  the  tissues  surrounding 
the  body  cavity  and  sew  themselves  thru  between  the  muscle  bundles  of 
the  thorax.  Whenever  Gordius  becomes  too  crowded  in  the  abdominal 
cavity  and  is  forced  into  the  thorax  it  passes  between  the  alimentary  canal 
and  the  thoracic  muscles,  but  never  between  the  muscle  bundles. 

The  parasite  does  not  appear  to  impair  very  greatly  the  health  of  the 
host,  for,  unless  the  infection  is  very  heavy,  the  infected  specimens  appear 
to  be  just  as  active  as  those  that  are  not  infected.  In  this  respect  the  infec- 
tion differs  from  an  infection  with  Mermis.  I  have  several  times  found 
specimens  infected  with  Mermithidae  to  be  sluggish. 

Observations  made  during  1914  seemed  to  indicate  that  the  infection 
was  confined  to  the  females  and  that  the  parasites  prevented  the  develop- 
ment of  the  ova.  No  attention  was  paid  to  the  sexes  of  the  hosts  during  the 
early  part  of  the  season,  but  during  October  only  females  were  found  to  be 
infected. 

During  the  infection  experiments  in  1916  it  became  evident  that  males 
as  well  as  females  became  infected,  and  later  when  hosts  were  collected  in 
the  field  for  examination  males  were  found  to  be  almost  as  heavily  infected 
as  females.  Of  711  males  examined  64  or  9  per  cent  were  infected  and 
of  440  females  examined  59  or  14  per  cent  were  infected.  Of  the  infected 
females  many  had  eggs,  but  usually  the  number  of  eggs  was  smaller  than 
in  normal  females,  aod  in  heavy  infections  with  older  worms  there  were 
usuaUy  no  eggs  present.  In  males  no  effect  on  the  reproductive  organs 
was  noted,  perhaps  mainly  because  it  is  more  difl&cult  to  detect  a  diminu- 
tion of  the  testes  than  of  the  ovaries. 

The  records  of  1914  showing  no  infection  in  males  remained  a  puzzle 
until  a  collection  was  made  on  October  14.  Of  10  males  collected  not  one 
was  infected,  while  in  11  females  seven  were  infected.    It  is  probable,  then, 


28  ILLINOIS  BIOLOGICAL  MONOGRAPHS  (148 

that  the  earlier  collections  of  1914  did  not  show  the  difference  in  infection 
between  males  and  females  that  was  noticed  later.  Whether  the  later 
difference  is  due  to  the  fact  that  infected  males  die  early  or  to  the  fact  that 
males  mature  and  lose  their  parasites  earlier  than  do  the  females  has  not 
been  determined. 

No  actual  observations  on  the  length  of  the  parasitic  period  have  been 
made,  and  since  the  data  bearing  on  this  subject  are  given  elsewhere,  this 
topic  may  be  left  for  later  discussion. 

The  period  during  which  parasites  become  mature  and  emerge  from 
their  hosts  lasts  from  early  September  until  late  October.  In  1914  no 
collections  were  made  before  September  21  and  only  a  few  hosts  were 
collected  before  September  23.  On  the  latter  date  78  hosts  were  collected 
and  several  parasites  escaped  before  the  collection  was  brought  to  the 
laboratory.  The  first  large  collection  in  1916  was  made  on  September  5 
and  jdelded  64  parasites  of  which  three  were  developing  the  brown  color. 
Of  8  parasites  obtained  on  September  6  one  was  developing  color,  20  obtain- 
ed September  7  were  all  white,  but  80  collected  September  8  included  5 
adults  ready  to  emerge.  The  other  limit  to  the  time  for  emergence  is  set 
by  the  death  of  the  last  host.  In  1914  the  last  big  collection  containing 
126  hosts,  was  made  on  October  3  and  yielded  17  parasites.  The  record 
contains  a  note  stating  that  one  of  the  specimens  was  the  youngest  obtained 
to  that  time  and  that  the  material  should  be  good  for  study  as  it  contained 
specimens  of  all  ages.  After  that  Orchelimum  vulgar e  became  more  and 
more  scarce.  On  October  17, 54  hosts  were  collected  and  were  found  to 
contain  mostly  mature  parasites,  but  a  few  that  were  not  fully  developed. 
In  three  further  collections  made  respectively  on  October  24,  29,  and  31, 
only  that  of  October  29  contained  a  single  female  of  Orchelimum  vulgare.  In 
1916  the  latest  collection  was  made  on  October  14  and  according  to  the 
records  one  parasite  was  still  quite  young.  At  that  time  the  hosts  were  so 
extremely  scarce  that  no  further  collections  were  made. 

Without  exception  I  have  found  the  parasites  escaping  with  the  an- 
terior end  first  from  a  region  near  the  anus  of  the  host.  In  all  I  have  seen 
more  than  two  dozen  specimens  of  Gordius  robustus  escape  from  their  hosts. 

The  mature  parasites  in  the  hosts  react  definitely  and  quickly  to  water. 
On  September  24,  1914  one  specimen  of  Orchelimum  vulgare  when  caught 
was  found  to  have  the  anterior  end  of  a  Gordius  protruded  at  its  posterior 
end.  When  the  host  was  dropped  into  the  bottle  and  thus  the  pressure  on 
the  abdomen  released  the  parasite  withdrew.  After  a  short  time  the  bottle 
was  partly  filled  with  water  and  the  parasite  emerged  within  one  minute. 
On  the  same  date  two  other  hosts  with  parasites  in  the  same  stage  were 
collected  and  placed  in  a  dry  bottle.  During  the  remainder  of  the  trip 
which  lasted  about  two  more  hours  the  parasites  remained  in  the  hosts.  In 
the  laboratory  the  hosts  were  placed  in  water  and  in  about  one  minute  the 


149]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  29 

parasites,  two  from  one  host  and  one  from  the  other,  had  escaped.  On 
October  19, 1914,  a  specimen  of  OrcM^'wMW  z;«/^flrg  which  had  been  collected 
on  October  15  and  kept  in  a  cage  in  the  meantime,  was  placed  in  water. 
Within  less  than  five  minutes  six,  specimens  of  Gordius  robustus  escaped. 
Similar  observations  were  made  several  times  after  that.  These  observa- 
tions show  that  Gordius  robustus  may  remain  for  a  long  time  in  the  body 
of  the  host  after  the  adult  state  has  been  reached  and  that  it  escapes  only 
under  favorable  conditions. 

ORGANOGENY 

On  account  of  the  large  amount  of  material  available,  including  speci- 
mens of  nearly  all  ages,  it  has  been  possible  to  follow  out  the  essential 
changes  that  take  place  from  the  time  the  larva  enters  the  host  to  the  time 
the  adult  emerges.  The  following  discussion  is  not  in  any  sense  to  be  the 
final  word  on  the  organogeny  of  Gordius  robustus,  but  on  account  of  the 
size  of  the  field  to  be  covered  it  seems  best  to  present  at  this  time  a  general 
account  of  the  changes  involved  and  to  leave  certain  particulars  for  further 
study  by  means  of  special  methods. 

Metamorphosis 

The  changes  that  tjrfce  place  soon  after  the  larva  has  entered  its  host, 
as  development  is  initiated,  hardly  justify  the  name  of  metamorphosis. 
There  is  no  encystment,  the  larva  remaining  active  even  a  short  time 
after  development  has  begun.  The  evidence  for  this  has  already  been 
given  in  the  discussion  of  the  infection  experiments.  Growth  begins 
at  about  the  same  time  in  all  of  the  tissues  of  the  body  and  parts  of  the 
proboscis  (Figs.  9,  11,  15,  50-53).  Development  in  the  proboscis  is  at* 
first  slower  than  in  the  body,  but  later  the  difference  disappears  and  it  is 
impossible  to  locate  the  division  between  body  and  proboscis  except  from 
the  location  of  the  partition  that  exists  between  the  two  in  the  larva 
(compare  Figs.  15  and  67).  The  parts  of  the  proboscis  that  do  not  enter 
into  later  development  are  the  cuticula  bearing  the  hooks  and  stylets  with 
the  underlying  hypoderm,  the  muscles,  and  the  column  of  cells  connecting 
the  stylets  with  the  partition  between  body  and  proboscis  (Figs.  57,67). 
The  cells  found  in  the  larva  at  the  anterior  end  of  the  intestine  (Fig.  20), 
increase  very  rapidly  in  size  at  first  (Figs.  11,  and  15,  )  but  later  are  fre- 
quently found  to  have  disintegrated  (Figs.  67,  68,  73)  and  are  probably  to 
be  regarded  as  a  special  organ  of  the  early  developmental  stages  and 
possibly  also  of  the  larva. 

Derivation  of  tissues 

Most  of  the  tissues  are  already  outlined  in  the  larva  and  merely  undergo 
further  development  in  the  parasitic  stage. 

Ectodermal  derivatives.  The  derivatives  of  the  ectoderm  of  the 
embryo  are  the  cuticula,  hypoderm  and  nervous  system. 

The  larval  cuticula  is  retained. 


30  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [ISO 

The  hypoderm  is  derived  directly  from  that  of  the  larva.  In  the  larva 
it  is  a  very  thin  layer  lying  immediately  beneath  the  cuticula  and  having 
only  very  few  nuclei  except  in  the  rudiment  of  the  nerve  cord  (Figs.  21,  49). 
Figures  14  and  20  are  somewhat  misleading  in  this  respect  as  it  was  im- 
possible to  determine  the  division  line  between  the  hypoderm  and  the 
underlying  muscles.  Even  in  the  young  parasitic  forms  the  hypoderm  is 
still  comparatively  thin  (Figs.  15,  51,  65,  66). 

The  nerve  cord  arises  as  a  thickening  in  the  hypoderm  (Figs.  15,  55, 58) 
along  the  ventral  side  as  indicated  by  the  two  rows  of  nuclei  in  the  larva 
(Figs.  14,  20,  56)  and  may  therefore  be  regarded  as  derived  directly  from 
the  nerve  rudiments  of  the  latter. 

The  derivation  of  the  brain  is  more  difficult  to  trace  and  an  exact 
determination  will  have  to  be  postponed  imtil  the  larva  can  be  studied 
more  thoroly.  It  arises  in  the  posterior  end  of  the  proboscis  rather  late  in 
development.  In  the  five  day  parasite  (Figs.  50-53)  and  also  in  the  six 
day  form  (Fig.  11)  its  location  is  not  yet  definitely  indicated.  In  the  nine 
day  form  (Fig.  15)  it  is  indicated  by  a  slight  enlargement  of  a  ring  of  cells 
around  the  proboscis  just  in  front  of  the  division  between  the  proboscis  and 
body.  In  the  12  day  stage  the  cells  have  become  enormously  enlarged, 
are  located  just  outside  of  the  muscle  strands  of  the  larval  proboscis  (Fig.  57) 
and  remain  connected  with  the  hypoderm  only  at  the  extreme  anterior  end 
and  on  the  ventral  side  (Figs.  67-69). 

Entodermal  derivatives.  The  young  larval  parasite  possesses  no  entoder- 
mal  derivative  except  the  intestine  and  this  develops  directly  from  that  of  the 
larva.  Its  development  is  at  first  very  rapid,  so  that  in  the  five  and  six 
day  stages  (Figs.  11, 50-52)  it  makes  up  a  large  part  of  the  bulk  of  the  para- 
site and  even  in  the  nine  and  twelve  day  stages  (Figs.  15,  66)  it  is  relative- 
ly enormous. 

Mesodermal  derivatives.  On  account  of  the  minuteness  of  all  the  cells 
and  the  indefinite  staining  reactions  it  has  been  impossible  to  connect 
the  mesodermal  derivatives  definitely  with  larval  structures.  It  is  possible, 
however,  to  outline  their  appearance  in  the  early  parasitic  stages. 

In  the  five  and  seven  day  stages  the  muscles  appear  as  minute  cells 
between  the  intestine  and  the  hypoderm  (Figs.  50, 51, 54).  In  the  nine  day 
stage  they  are  dearly  outlined  as  a  continuous  layer  of  elongated  cells  lying 
just  inside  of  the  hypoderm  (Fig.  55). 

Since  the  parenchyma  appears  very  late  its  origin  will  be  taken  up  in 
the  discussion  of  the  later  development. 

The  reproductive  organs  appear  in  the  five  day  stage  as  a  double  row  of 
cells  on  each  side  of  the  intestine,  slightly  dorsal  in  position,  along  the  main 
part  of  the  body  (Figs.  50,  51).  In  the  nine  day  stage  (Fig.  55)  and  more 
clearly  in  the  twelve  day  stage  (Fig.  66)  they  appear  as  two  definite  ridges, 
just  inside  of  the  muscle  layer,  dorso-lateral  to  the  intestine,  and  extend 
almost  the  entire  length  of  the  body. 


151]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  31 

Later  development 

From  the  nine  day  stage  (Fig.  15)  the  parasite  passes  over  into  a  spiral 
form  and  this  soon  straightens  out  into  a  loose  spiral  and  finally  a  straight, 
cylindrical  form  with  rounded  ends.  The  straight  form  is  often  reached  in 
twelve  days.  After  that  the  parasites,  tho  usually  coiled  in  the  body  of  the 
host,  are  straight  when  relaxed  in  salt  solution.  In  this  they  differ  from 
parasitic  Mermithidae  which  when  relaxed,  take  the  form  of  a  helix.  To 
the  28  day  stage  and  beyond,  the  parasites  are  so  transparent  that  it 
requires  a  dark  background  to  see  them.  Later  stages  are  white  until  the 
adult  color  develops. 

Development  takes  place  uniformly  thruout  the  length  of  the  body. 
This  is  shown  in  the  stage  of  development  of  the  nerve  cord  in  figurers 
29  and  72,  taken  from  the  middle  and  posterior  end  of  the  same  specimen 
and  in  the  development  of  the  cuticula  in  figures  108  and  107  taken 
respectively  from  the  anterior  end  and  posterior  end  of  a  male  in  which 
the  fibrous  layer  of  the  aduU  cuticula  was  in  the  process  of  formation. 

In  the  following  discussions  the  different  tissues  and  organs  will  be 
taken  up  separately  and  their  development  traced  to  the  adult  structure. 
Comparisons  with  the  results  obtained  by  other  authors  will  be  taken  up 
in  a  separate  division  of  this  report  after  the  description  of  the  different 
structures  has  been  completed. 

Cuticula.  Earlier  stages  are  covered  only  by  the  larval  cuticula  since 
the  adult  cuticula  appears  very  late  in  development. 

Larval  cuticula.  With  the  initiation  of  development  there  comes 
a  decided  increase  in  the  permeability  of  the  cuticula.  While  it  is  almost 
impossible  to  dehydrate  and  mount  free  living  larvae  without  having  them 
collapse,  the  early  parasitic  stages  may  be  mounted  with  comparative  ease. 
Together  with  this  increase  in  the  permeability  comes  an  increase  in  the 
thickness  of  the  cuticula.  While  in  the  larva  and  the  very  young  form  it 
appears  only  as  a  very  fine  line  when  magnified  800  times,  in  the  twelve  day 
stage  it  appears  as  a  much  heavier  line  at  a  magnification  of  only  500  times. 
Actual  measurements  give  values  of  about  0.35/*  foi  the  larva,  0.55/i  for  the 
five  day  stage,  and  0.7 fi  for  the  twelve  day  stage.  This  increase  in  thickness 
continues  at  about  the  same  rate  until  the  time  the  nerve  cord  separates 
from  the  hypoderm  and  growth  has  already  taken  place  in  part  of  the  germ 
cells.  At  that  time  the  diameter  is  nearly  two  micra.  Soon  after  that  there 
appears  directly  beneath  the  cuticula  a  finely  granular  layer,  stainable 
with  iron  hematoxylin  and  alkaline  methylene  blue.  There  now  appears 
between  the  larval  cuticula  and  the  granular  layer  a  more  homogeneous 
layer  (Figs.  85,  112)  not  stainable  in  iron  hematoxyhn  (Figs.  108,  117) 
but  heavily  stained  by  aniline  blue  in  Mallory's  connective  tissue  stain. 
The  larval  cuticula  remains  connected  with  the  granular  layer  by  very 
fine  strands   (Figs.   38).     At  times  there  appear  in   this  layer  larger 


32  ILUNOIS  BIOLOGICAL  MONOGRAPHS  1152 

amorphous  bodies  which  are  probably  due  to  the  action  of  the  killing  agent. 
This  homogeneous  layer,  as  it  may  be  called,  attains  a  diameter  of  about 
10/i  at  the  time  the  tissues  of  the  parasite  have  reached  their  full  develop- 
ment and  then  begins  to  disintegrate.  By  the  disintegration  of  this 
layer  the  larval  cuticula  becomes  loosened  from  the  underlying  granular 
layer  (Fig.  39),  soon  becomes  torn,  and  is  sloughed  off  from  the  body 
of  the  parasite  when  it  is  ready  to  leave  the  host.  When  fully  developed 
parasites  are  taken  from  their  hosts  pieces  of  the  larval  cuticula  are 
often  seen  trailing  from  one  or  both  ends  like  transparent  threads.  The 
larval  proboscis  which  has  been  lying  just  beneath  the  larval  cuticula 
(Fig.  73)  is  also  shed  at  this  time.  In  some  cases  the  deeper  part  of  the 
intervening  layer  does  not  become  disintegrated  by  the  time  the  larval 
cuticula  is  shed  and  remains  for  a  short  time  attached  to  the  granular 
layer,  but  ultimately  it  becomes  entirely  removed.  The  structure  of  the 
larval  cuticula  is  homogeneous  thruout. 

-  Adult  cuticula.  The  earliest  beginning  of  the  adult  cuticula  is  the 
formation  of  the  granular  layer  under  the  larval  cuticula  as  described  in 
the  previous  section.  This  granular  layer,  which  increases  somewhat  in 
thickness,  but  never  has  any  very  definite  boundaries,  forms  the  layer 
known  as  the  homogeneous  cuticula  of  the  adult.  The  granules  become 
crowded  closer  together  so  that  they  are  not  easily  distinguishable. 

The  fibrous  cuticula  of  the  adult  appears  as  a  differentiation  of  the 
cytoplasm  of  the  hypoderm  some  time  after  the  formation  of  the  granular 
layer,  when  the  intervening  homogeneous  layer  has  already  reached  nearly 
half  its  final  diameter  (Figs.  112,  41,  35,  116).  Thruout  development  the 
fibrous  cuticula  consists  of  fibrous  strands  connecting  the  granular  layer 
with  the  h)^oderm  and  of  an  intervening  matrix  (Fig.  43,  119).  The 
intervening  matrix  is  under  the  most  favorable  conditions  resolvable 
into  layers  of  fibers  perpendicular  to  the  radiating  strands  and  forming 
nodules  at  the  intersections  with  those  strands  (Fig.  43).  The  fibers 
composing  these  layers  in  the  matrix  are  the  rudiments  of  the  ultimate 
diagonally  intersecting  fibers  of  the  adult  cuticula.  The  nodules  at  first 
appear  to  produce  a  thickening  of  the  radiating  fibers  but  later  fuse 
along  the  diagonal  fibers  and  separate  from  each  other  along  the  radiat- 
ing fibers  to  form  the  heavy  fibers  of  the  adult  cuticula.  The  layers  of 
diagonal  fibers  are  not  formed  in  a  regularly  alternating  series,  but  two 
layers  in  one  direction  alternate  with  one  in  the  other  (Fig.  38).  This  fact 
can  be  determined  only  on  diagonal  sections  made  parallel  to  the  fibers  of 
one  of  the  layers.  The  number  of  layers  of  intersecting  fibers  is  variable, 
but  near  the  middle  of  the  body  it  is  about  45  (Fig.  38)  and  even  on  the 
prongs  of  the  fork  of  the  male  it  is  seldom  less  than  30  (Figs.  121-123). 
Since  in  two  adjacent  layers  of  parallel  fibers  the  fibers  of  one  are  of  the  same 
diameter  as  those  of  the  alternating  layer,  but  those  of  the  other  are  much 


153]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  33 

thinner,  low  magnification  shows  the  two  adjacent  layers  of  heavy  fibers  as 
a  single  dark  layer  and  between  two  such  dark  layers  the  thinner  fibers  as  a 
lighter  layer,  thus  giving  the  cuticula  the  appearance  of  being  composed 
of  ten  to  fifteen  dark  layers  (Fig.  124). 

The  adult  cuticula,  macerated  in  nitric  acid  and  separated  into  thin 
layers,  shows  clearly  under  low  magnification  the  rhomboids  formed  by  the 
intersection  of  the  coarser  lines  (Fig.  5)  and  under  high  magnification  the 
finer  intersecting  fibers  (Fig.  4).  The  coarser  lines  enclosing  the  rhomboids 
are  due  to  a  slight  increase  in  the  thickness  of  the  fibers  as  well  as  in  the 
pigmentation. 

The  bristles  of  the  adult  cuticula,  when  they  first  become  evident,  are 
heavy  radiating  strands  connecting  the  larval  cuticula  with  the  hypoderm 
(Figs.  38,  40).  At  first  they  are  thick  and  translucent,  but  later  they 
become  shrunken  and  opaque,  and  it  is  impossible  to  trace  them  beneath 
the  first  layer  of  the  fibrous  cuticula.  At  the  time  of  moulting  they 
becofne  detached  from  the  larval  cuticula  and  remain  attached  to  the 
surface  of  the  adult  cuticula.  The  bristles  pass  thru  the  granular  layer 
(Fig.  44)  and  consequently  are  not  covered  by  the  homogeneous  cuticula 
of  the  adult. 

The  postcloacal  ridge  of  the  male  is  formed  by  elongated  cells  in  the 
hypoderm  (Figs.  37,  60,  61)  and  appears  as  a  thickening  in  the  granular 
layer.  In  the  adult  it  appears  to  be  continuous  with  the  homogeneous 
cuticula  and  on  cross  section  has  the  appearance  of  a  stout  hook  set  upon  a 
projecting  base  of  the  fibrous  cuticula  and  curved  slightly  backward  and 
inward  (Fig.  98). 

Over  the  anterior  end  the  fibrous  cuticula  develops  in  the  normal  way, 
but  is  not  so  thick  as  elsewhere.  Later  the  fibres  become  more  closely 
packed  together,  all  granular  substances  disappear,  and  the  cuticula  under 
the  white  area  becomes  nearly  homogeneous  and  transparent. 

During  the  entire  period  of  development  the  layers  of  the  cuticula  are 
pure  white.  Pigmentation  begins  when  the  homogeneous  layer  underlying 
the  larval  cuticula  has  already  begun  to  disintegrate.  Pigmentation  begins 
first  in  the  dark  ring  behind  the  anterior  white  area.  It  next  delineates  the 
dorsal  and  ventral  bands,  beginning  at  the  anterior  end  and  passing  back- 
ward. By  the  time  these  bands  are  shown  on  about  the  anterior  fourth 
of  the  body,  pigmentation  of  the  rest  of  the  cuticula  begins  at  the  anterior 
end  and  slightly  later  also  at  the  posterior  end.  At  this  end  also  the  dark 
bands  appear  first,  but  are  never  so  clearly  outlined  as  at  the  anterior  end. 
The  bands  from  the  two  ends  soon  come  together  slightly  posterior  to  the 
middle  of  the  body  and  the  pigmentation  of  the  rest  of  the  cuticula  pro- 
ceeds in  the  same  order.  In  case  of  all  specimens  observed  leaving  Iheir 
hosts  the  pigmentation  could  not  be  distinguished  from  that  of  free  living 
specimens.    If  specimens  in  which  the  pigmentation  is  not  complete  are 


34  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [154 

removed  from  their  hosts  the  intensity  of  the  pigmentation  doeg  not  appre- 
ciably increase  in  the  free  state.  Several  such  specimens  were  observed  for 
short  periods  and  one  female  with  little  pigmentation  except  the  dark  ring 
and  bands  was  removed  from  the  host  on  September  6,  1916,  and  kept  aUve 
in  an  aquarium  until  the  beginning  of  March,  1917,  with  no  appreciable 
increase  in  pigmentation.  The  specimen  at  that  time  died  from  an  attack 
of  fungu^. 

Hypoderm.  In  the  specimens  five  day  old  the  hypoderm  is  already 
dearly  distinguishable  as  a  layer  of  flattened  cells,  slightly  thickened  in  the 
region  of  the  nerve  cord,  and  lying  just  beneath  the  cuticula  (Figs.  50,  51). 
Partly  by  the  thickening  of  the  layer,  but  chiefly  by  the  rapid  multiplica- 
tion of  the  cells,  the  latter  have  become  cuboidal  when  the  nine  day  stage 
has  been  reached  (Fig.  55).  By  a  continuation  of  the  multiplication  and  the 
increase  of  the  thickness  of  the  layer  the  cells  soon  come  to  be  columnar  in 
character.  This  condition  is  clearly  shown  at  the  ends  of  the  specimens 
in  the  twelve  day  stage,  and  appears  over  the  entire  body  at  slightly  later 
stages  (Figs.  84,  86).  Multiplication  of  the  cells  appears  to  be  complete  by 
the  time  growth  begins  in  the  germ  cells  (Fig.  86)  and  further  development 
depends  upon  growth.  In  some  cases  there  is  a  secondary  flattening  of  the 
cells  before  the  development  of  the  adult  cuticula  is  initiated  (Fig.  87),  but 
whether  this  secondary  flattering  occurs  or  the  cells  remain  columnar 
(Fig.  99),  the  small,  round  nuclei  (Figs.  71,  73)  become  enlarged  and 
flattened  in  a  direction  parallel  to  the  surface  of  the  specimen  (Figs.  42, 
99).  The  enlargement  and  flattening  occur  by  the  flowing  together  of 
several  chromophil  centers  into  one  nucleus,  the  accumulation  of  achroma- 
tic substance  around  these  centers,  and  the  development  of  a  definite 
nuclear  membrane  surrounding  both  (Figs.  70,  127).  The  chromatic 
centers  remain  as  distinct  nucleoli  within  the  larger  nuclei.  As  the 
adult  stage  is  approached  the  nucleoh  increase  in  size  and  become  more 
diffused  so  as  to  occupy  more  or  less  completely  the  entire  space  within 
the  nuclear  membrane.  At  the  same  time  the  nucleus  shrinks  and  becomes 
excessively  flattened,  crowding  together  the  nucleolar  matter  into  a  dense 
mass  (Fig.  124). 

Altho  in  cross  sections  of  the  hypoderm  the  ceUs  appear  to  form  a 
syncytium  with  the  cell  boundaries  merely  indicated  here  and  there 
(Figs.  41,  73),  tangetial  sections  and  preparations  of  separated  pieces 
of  hypoderm  show  distinctly  the  cell  outlines  (Figs.  127, 128).  Such  pre- 
parations, however,  show  that  the  cell  boundaries  are  not  complete,  the 
cells  remaining  connected  with  each  other  by  numerous  protoplasmic 
strands.  During  the  earliest  stages  of  the  formation  of  the  fibrous  cuticula 
there  appears  within  the  outer  part  of  the  hypoderm  a  system  of  canals 
surrounding  the  cells  (Fig.  41)  and,  at  the  intersections,  sending  out 
branches  to  their  bases. 


155]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  35 

The  hypoderm  is  always  of  greater  diameter  at  the  ends  of  the  body 
than  in  the  middle.  The  elongated  cells  forming  the  postcloacal  ridge  of 
the  male  have  already  been  mentioned.  Other  modifications  of  the  hypo- 
derm  will  be  taken  up  in  the  next  topic. 

Nervous  system.  The  nervous  system  consists  of  brain,  ventral  cord, 
cloacal  ganglion,  peripheral  fibers  and  nerve  cells  located  in  various  parts 
of  the  hypoderm. 

Central  nervous  system.  The  very  early,  appearance  of  the  central 
nervous  system  has  already  been  described.  In  the  description  of  the  later 
development  each  part  will  be  taken  up  separately. 

As  stated  in  a  previous  section,  the  brain  is  outlined  at  first  as  a  ring  of 
cells  in  the  hypoderm  of  the  proboscis.  It  soon  separates  from  the  hypo- 
derm, remaining  connected  with  it  only  at  the  anterior  end  and  the  ventral 
side  (Figs.  57,  67-69).  It  consists  at  this  time  of  a  few  large  cells  situated 
just  in  front  of  the  partition  between  the  region  developed  from  the  larval 
proboscis  and  that  developed  from  the  body  of  the  larva.  The  cells  com- 
pletely surround  the  larval  muscles  and  the  strand  that  connects  the  sti- 
lets  with  the  partition  in  the  larva.  These  large  cells  remain  permanently 
in  that  position  (Figs.  73,  74)  while  the  rest  of  the  brain  develops  in  front 
and  around 'them,  most  of  the  later  cells  appearing  antero-ventrad  to  the 
original  group.  By  the  growth  of  the  anterior  region  the  larval  connecting 
strand  becomes  stretched  out  and  torn,  the  major  part  of  it  usually  remain- 
ing in  the  base  of  the  brain,  while  the  armature  of  the  proboscis  is  carried 
forward  and  pushed  out  of  the  hypoderm  at  the  anterior  end  (Figs.  73, 
22,  23).  The  strand  in  the  base  of  the  brain  later  disintegrates,  leaving  an 
open  space  (Fig.  74).  At  the  time  the  cells  have  reached  their  full  develop- 
ment the  original  group  forms  the  postero-dorsal  part  of  the  brain  (Figs. 
81-83),  while  the  other  cells,  mostly  smaller  in  size,  surround  the  rest  of 
the  brain  and  form  a  heavy  mass  at  the  ventral  side  continuous  with  the 
cells  of  the  ventral  cord  (Figs.  73,  81-83).  The  central  core  of  the  brain 
is  occupied  chiefly  by  fibres  with  a  few  scattered  cells.  From  the  ventral 
cell  mass  a  group  of  cells  projects  dorsad  into  the  anterior  part  of  the  fibre 
mass  and  tends  to  become  separated  by  intervening  fibres  from  the 
underlying  cells.  Ventral  and  slightly  posterior  to  this  group  of  cells 
is  a  large,  definitely  outlined  cross  commissure  (Fig.  74)  dividing  at  each 
end  into  a  ventral  and.  a  dorsal  branch.  The  cells  of  the  brain  appear 
to  be  multipolar  but  that  fact  has  not  been  definitely  established. 

The  fibres  in  the  brain  pass  in  all  conceivable  directions,  and  many 
of  them  are  directly  continuous  with  those  of  the  cord.  At  the  anterior 
end  under  the  white  area  and  part  of  the  dark  ring  the  hypoderm  is 
very  much  thickened,  most  of  the  cells  are  modified  into  bipolar  nerve 
cells  like  those  which  connect  the  ventral  cord  to  the  hypoderm  in  the  rest 
of  the  body,  and  on  the  ventral  side  these  fibres  pass  directly  over  into 
the  connecting  fibres  of  the  cord. 


36  ILLINOIS  BIOLOGICAL  MONOGRAPHS  {156 

The  ventral  cord  arises  as  a  thickening  in  the  hypoderm,  as  has  already 
been  shown,  but  later  becomes  separated  from  it,  passing  inward  even 
beyond  the  muscle  layer  and  remaining  connected  with  the  hypoderm 
only  by  a  single  row  of  cells  (Figs.  58, 105). 

The  cells  that  later  make  up  the  nerve  cord  at  first  appear  as  two  rows 
of  larger  cells  in  the  hypoderm  (Fig.  56)  corresponding  to  the  two  rows  of 
nuclei  on  the  ventral  side  of  the  larva.  Even  in  later  stages  these  two 
rows  of  cells  remain  clearly  distinguishable  altho  they  crowd  each  other 
so  that  they  come  to  lie  alternately  one  behind  the  other  and  do  not  usually 
show  in  a  single  section.  Between  these  two  rows  of  cells  and  on  each 
side  of  them  appear  very  early  in  development  three  longitudinal  fiber  tracts 
(Figs.  56, 58),  which  are  the  rudiments  of  the  three  main  fiber  tracts  of  the 
nerve  cord.  Nerve  cells  later  appear  under  these  fibre  tracts  and  on  the  two 
sides  of  them  (Fig.  88),  separating  the  tracts  entirely  from  the  rest  of  the 
hypoderm.  By  the  growth  of  the  cells  under  the  median  tract,  that  is 
pushed  out  beyond  the  two  lateral  tracts,  and  the  division  between  the  two 
rows  of  cells  becomes  nearly  obliterated.  The  cord,  after  separating  from 
the  hypoderm,  has  in  cross  section  the  shape  of  a  loop  or  fan  with  rounded 
corners,  the  cells  forming  the  base  and  projecting  far  into  the  interior. 

It  has  been  impossible  to  determine  the  structure  of  the  smaller  cells. 
The  larger  cells,  where  their  structure  could  be  made  out,  have  been  found 
to  be  bipolar,  giving  off  one  fibre  to  the  longitudinal  tract  and  one  to  the 
dorsal  border  of  the  cord  (Fig.  139).  The  longitudinal  fibres  as  well  as  the 
radiating  fibres  stain  very  deeply  with  iron  hematoxylin  (Figs.  105, 106, 114) 
but  the  structures  shown  throw  little  light  on  the  physiology  of  the  nerve 
cord.  The  longitudinal  fibres  have  been  traced  only  for  short  distances 
(Fig.  102).  In  a  number  of  cases  fibres  have  been  found  to  pass  over  cross- 
wise from  one  part  of  the  cord  to  the  other  (Fig.  114).  Both  the  radiating 
fibres  and  the  crossing  fibres  enlarge  slightly  toward  the  periphery  and  end 
abruptly  at  the  edge  of  the  cord. 

In  later  stages  the  connection  between  the  nerve  cord  and  hypoderm 
consists  of  spindle-shaped*,  bipolar  cells  placed  in  close  succession  one  behind 
the  other  in  a  single  row,  with  nowhere  an  indication  of  a  ganglion  (Fig.  45). 

In  the  male  the  ventral  cord  separates  into  two  branches  at  the  posterior 
end,  a  branch  passing  into  each  prong  of  the  fork  (Fig.  98)  and  ultimately 
disappearing  in  the  hypoderm  (Fig.  36).  Beginning  at  about  the  point 
where  the  connection  between  hypoderm  and  cord  becomes  divided  and 
passing  backward  to  the  cloacal  musculature  there  is  an  enlargement  of  the 
cord,  the  cloacal  ganglion  (Figs.  101, 102).  It  consists  chiefly  of  an  increase 
of  the  fibrous  part  of  the  cord  and  hardly  deserves  the  name  of  ganglion. 

In  the  female  an  enlargement  of  the  cord  occurs  near  the  posterior 
end,  opposite  the  cloacal  musculature  (Fig.  92),  while  the  cord  is  passing 
into  the  hypoderm.    This  appears  as  an  enlargement  of  the  cellular  part  of 


157]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA 7  37 

the  cord  with  fibres  passing  into  the  musculature  and  the  hypoderm 
surrounding  the  cloacal  aperture. 

Peripheral  nervous  system.  The  ordinary  methods  of  technic  show 
very  little  of  the  peripheral  nervous  system  and  consequently  it  will 
have  to  be  dismissed  at  this  time  with  a  few  passing  remarks.  In  a  few 
adults  stained  with  iron  hematoxylin  nerve  fibres  were  shown  passing  from 
the  nerve  cord  into  the  hypoderm  and  could  also  be  traced  for  some  dis- 
tance in  the  hypoderm  (Figs.  115, 118,  120).  The  fibres  pass  directly  into 
the  hypoderm  and,  some  distance  from  the  cord,  are  seen  to  lie  well  within 
the  hypoderm  mesad  from  the  nuclei.  At  the  time  of  the  formation  of  the 
cuticula  it  is  u^ally  possible  to  detect  flask-shaped  cells  in  the  inner  part 
of  the  h5^oderm  (Figs.  42,  129)  and  in  a  few  cases  fibres  passing  outward 
from  these  cells  or  parallel  to  the  surface  of  the  hypoderm. 

Digestive  system.  The  digestive  system  consists  only  of  a  straight  tube 
beginning  near  the  anterior  end  and  opening  at  the  posterior  end.  Neither 
mouth  nor  esophagus  is  present  in  this  species  at  any  stage  of  development. 
The  structures  that  might  be  mistaken  for  mouth  and  esophagus  have  al- 
ready, in  the  discussion  of  the  brain,  been  shown  to  be  merely  the  spaces 
previously  occupied  by  parts  of  the  larval  proboscis. 

As  in  the  larva  (Fig.  20)  so  in  the  young  parasitic  forms,  the  anterior 
part  of  the  intestine  consists  of  a  solid  mass  of  cells  (Figs.  11,  15),  and  the 
lumen  begins  behind  this  cell  mass.  Later  this  cell  mass  disinte- 
grates, as  is  shown  in  some  specimens  of  the  twelve  day  stage  (Figs.  67, 68). 
By  the  time  the  twenty-eight  day  stage  has  been  reached  the  space  left  by 
the  disintegration  of  those  cells  has  been  filled  by  mesenchyme,  thus  the 
brain  and  intestine  have  become  distinctly  separated  and  the  lumen  of  the 
intestine  is  closed  by  a  single  layer  of  cells.  In  some  cases,  however,  the 
mass  of  cells  does  not  disintegrate  completely  until  a  much  later  stage  is 
reached  (Fig.  73).  In  either  case  the  mesenchyme  cells  soon  invade  the 
region  between  the  intestine  and  the  brain,  so  that  in  the  later  stages  the 
two  come  to  be  separated  by  a  solid  mass  of  parenchyma  equal  in  length  to 
more  than  half  the  diameter  of  the  body  (Fig.  74). 

Whether  or  not  there  is  in  the  larva  and  young  parasite  an  outlet  of  the 
cell  mass  thru  the  proboscis,  can  not  be  determined  from  the  material  at 
hand.  A  tube  can  be  traced  from  the  anterior  end  to  the  base  of  the  stylets 
(Fig.  47)  and  in  some  cases  appears  to  be  indicated  in  the  connecting 
strand  behind  the  stylets,  but  on  account  of  the  extreme  minuteness  of 
the  structures  as  compared  with  the  thickness  of  the  sections  it  is  impossible 
to  make  a  definite  determination.  But,  even  if  there  is  a  tube  leading 
from  the  end  of  the  stylets  to  the  cell  mass,  it  never  passes  thru  the  cell 
mass  to  the  lumen  of  the  intestine. 

From  the  early  stages  until  the  adult  cuticula  has  been  nearly  completed 
the  walls  of  the  intestine  consist  of  a  syncytium  of  heavy  cells  with  large 


38  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [158 

nuclei  and  with  the  cell  boundaries  only  very  faintly  indicated  (Figs.  50,  72, 
73,75,79,84,86,106).  Around  the  outside  of  the  intestine  is  a  heavy 
membrane  (Fig.  77),  easily  demonstrated  when  stained  with  Mallory's 
connective  tissue  stain.  The  inner  edge  of  the  wall  is  frequently  dififerenti- 
ated  into  a  loose,  porous  or  spongy  structure,  with  no  definite  membrane 
on  the  inner  surface  (Fig.  106).  During  the  early  part  of  the  formation 
of  the  fibrous  cuticula  the  cells  of  the  intestine  begin  to  decrease  in  size, 
in  the  adults  they  are  excessively  shrunken,  and  by  the  time  the  reproduc- 
tive products  have  been  discharged  there  is  little  left  but  the  skeletal  struc- 
ture of  the  cells  (Fig.  46). 

At  the  posterior  end  the  intestine  in  the  very  young  forms  opens  slightly 
ventral  (Figs.  11, 15),  but  by  the  twelve  day  stage  has  become  nearly  ter- 
minal (Figs.  63,  64).  At  that  stage  diverticula  are  formed  at  the  points 
where  the  seminal  receptacle  and  oviducts  in  the  female  and  the  sperm 
ducts  in  the  male  later  enter  the  cloaca  (Figs.  64, 65).  The  part  of  the  intes- 
tine behind  these  diverticula  is  in  the  young  stages  lined  by  a  heavy  mem- 
brane and  in  the  adult  condition  lined  by  the  homogeneous  cuticula 
(Fig.  78)  and  must  be  regarded  as  consisting  of  invaginated  hypoderm. 
In  the  female  the  opening  of  the  intestine  remains  terminal,  but  in 
the  male  it  is  again  shifted  to  the  ventral  side.  The  lobes  of  the  fork 
first  grow  out  beyond  the  cloacal  aperture  (Fig.  59)  and  then  by  an  over- 
growth of  the  dorsal  wall  the  aperture  is  turned  to  the  ventral  side  (Figs. 
60,  61).  The  larval  cuticula  does  not  enter  the  space  between  the  prongs, 
but  leaves  this  space  to  be  filled  out  by  a  substance  similar  to  the  homo- 
geneous intermediate  layer,  the  intestine  opening  terminally  thru  a  passage 
in  this  substance  (Figs.  36,  60). 

Excretory  system  At  no  stage  in  the  development  is  there  present  any 
trace  of  an  excretory  system  corresponding  in  any  way  to  the  excretory 
systems  found  in  other  animals. 

Circulatory  system.  There  exists  no  definite  circulatory  system,  but 
there  are  present  at  all  stages  in  development  spaces  in  diflFerent  parts 
of  the  body  that  undoubtedly  aid  in  the  distribution  of  the  body  fluids. 
Very  early  the  intestine  becomes  surrounded  by  an  open  space,  remaining 
attached  to  the  other  tissue  only  on  the  ventral  side.  This  space  is  later 
invaded  to  a  great  extent  by  the  parenchyma  but  is  seldom  entirely 
eliminated.  It  is  the  only  space  that  is  usually  present.  In  the  females  a 
second  space  later  appears  on  the  dorsal  side  between  the  points  of  attach- 
ment of  the  ovaries.  These  spaces  usually  do  not  approach  the  ends  of  the 
body  which  are  filled  with  parenchyma. 

Muscles.  In  the  very  young  forms  the  muscles  appear  as  a  layer 
of  longitudinally  arranged,  spindle-shaped  cells,  lining  the  hypoderm 
(Fig.  67) .  The  cells  are  at  first  rounded  in  cross  section  but  soon  become 
flattened  by  crowding  against  each  other  so  that  they  appear  as  columnar 


159]  UFE  HISTOR Y  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  39 

cells  in  cross  section  with  the  nucleus  lying  close  to  the  inner  edge.  As 
development  goes  on  the  cells  become  more  and  more  flattened  and 
elongated  (Figs.  112,  117).  When  viewed  from  the  edge  the  cells  take  on 
the  appearance  of  very  much  elongated  spindles  with  the  two  ends  running 
out  into  fine  points.  From  the  side  they  appear  as  long  blades  with  one 
edge  straight  and  the  other  rounded  at  the  ends  (Fig.  126).  When  in  posi- 
tion the  blades  are  placed  with  the  straight  edge  against  the  hypoderm  and 
the  nucleus  is  located  in  the  middle  of  the  opposite  edge.  The  ends  can 
easily  be  detected  ^n  cross  section  lying  in  the  outer  half  of  the  muscle 
layer  (Fig.  112).  The  nucleus,  at  first  nearly  round,  later  comes  to  be  a 
very  much  elongated,  flattened,  oval  body,  lying  either  at  the  inner  edge 
or  near  the  inner  edge  of  the  cell,  and  occupying  nearly  the  whole  diameter 
of  the  cell  at  that  point  (Fig.  107). 

The  cytoplasm  of  the  cell  at  first  does  not  appear  different  from  that 
of  other  cells  but  later  there  is  formed  a  deeply  staining  granular  substance 
extending  from  the  nucleus  to  the  outer  edge  of  the  cell;  this  substance 
finally  forms  longitudinal  fibrils  which  arrange  themselves  in  a  continuous 
layer  around  the  inner,  spongy  cytoplasm  and  the  nucleus  (Figs.  43,  105, 
112,  124,  126).  The  fibrils  are  not  of  homogeneous  structure,  but  are 
composed  of  serially  arranged  granules.  l^ — 

The  cells  at  first  are  contiguous,  but  at  the  time  the  heavy  walls  appear  '^ 

in  the  parenchyma  a  substance  having  the  same  appearance  and  staining 
reactions  as  those  walls  surrounds  each  cell,  so  that  the  cells  become 
separated  from  each  other,  from  the  hypoderm  and  from  the  parenchyma 
(Fig.  116).  At  the  ends  of  the  body  the  muscles  gradually  lose  their 
characteristic  structure  and  pass  over  into  the  parenchyma. 

At  the  time  of  the  discharge  of  the  reproductive  products  the  muscles 
begin  to  disintegrate  slowly  from  the  inner  edge.  In  some  specimens 
sectioned  this  process  had  consumed  nearly  the  whole  muscle  cells  (Figs. 
46,  124). 

The  cloacal  musculature  of  the  male  consists  of  radiating  fibres  around 
the  cloaca  and  circular  fibres  surrounding  the  sperm  ducts  just  before  they 
enter  the  cloaca  (Figs.  96,  97).  In  the  early  stages  the  cells  are  not 
differentiated  from  parenchyma  cells,  but  later  they  become  very  much 
elongated  and  in  the  adults  lack  the  heavy  cell  walls  that  are  found  in  the 
parenchyma.  The  radiating  fibers  arise  from  the  dorsal  and  lateral  walls 
of  the  cloaca  and  extend  for  the  main  part  in  a  dorso-lateral  direction. 

The  cloacal  musculature  of  the  female  consists  of  a  heavy  circular  muscle 
forming  the  constriction  between  the  cloaca  and  the  sperm  receptacle 
(Fig.  94)  and  weaker  circular  muscles  around  the  oviducts.  The  fibers 
are  similar  to  those  of  the  male  cloacal  musculature.  There  is  also  present 
a  heavy  group  of  circular  fibers  around  the  posterior  end  of  the  cloaca, 
and  a  sheet  of  longitudinal  fibers  surrounding  the  glandular  part  of  the 


40  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [160 

doaca.  These  fibers  are  intermediate  in  structure  between  muscle  fibers 
and  parenchyma  cells.  They  are  elongated,  closely  compact,  but  do  not 
stain  as  deeply  as  muscle  cells  and  possess  walls  nearly  as  heavy  as  those 
of  the  parenchyma. 

Parenchyma  and  mesenteries.  The  parenchyma  arises  first  as  spindle- 
shaped  or  multipolar  mesenchyme  cells  (Figs.  63,  67-69).  Most  of  the 
cells  appear  to  arise  at  the  ends  of  the  body,  but  a  few  cells  are  also  found 
in  the  intermediate  region  at  a  very  early  stage  and  may  arise  there.  In 
the  twelve  day  stage  many  of  the  cells  are  not  distinguishable  from  muscle 
cells  between  which  they  are  frequently  inserted,  and  even  in  much  later 
stages  the  distinction  between  the  two  kinds  of  cells  is  not  always  clear. 
The  cells  remain  generalized  for  a  long  time  and  are  scarcely  distinguishable 
from  cells  that  form  the  rudiments  of  other  organs  (Fig.  109). 

The  multiplication  of  the  cells  takes  place  very  rapidly.  In  the  male 
they  often  fill  completely  the  spaces  between  the  organs.  Except  at  the 
ends,  where  they  form  a  solid  mass  from  the  beginning,  they  first  form  an 
irregular  layer  lining  the  muscles  and  the  nerve  cord  and  forming  triradiate 
septa  which  enclose  the  germ  cells.  Ventral  to  the  germ  cells  the  cavity 
still  remains  and  the  intestine  is  attached  to  the  layer  of  cells  over  the  nerve 
cord  (Fig.  75).  By  further  multiplication  of  the  cells  the  germ  cells  become 
farther  removed  from  the  muscles  and  all  or  nearly  all  of  the  space  becomes 
invaded  (Figs.  107,  108). 

In  the  females  the  multiplication  of  the  cells  is  not  so  prolific.  The 
layer  lining  the  muscles  and  nerve  cord  and  holding  the  intestine  in  place 
is  formed  as  in  the  males,  but  it  passes  between  the  muscles  and  the  ovaries 
only  at  the  end  of  the  body,  leaving  the  ovaries  in  contact  with  the  muscles 
thruout  nearly  their  whole  length.  A  few  mesenchyma  cells  enter  between' 
the  ovaries  and  others  are  scattered  thruout  the  body  at  different  places, 
but  there  are  no  definite  layers  enclosing  the  germ  cells  (Figs.  76,  79,  86). 
By  the  later  growth  of  the  eggs  nearly  all  of  the  spaces  in  the  body  are 
eliminated. 

A  short  time  before  the  adult  cuticula  is  formed  the  cells  become  sur- 
rounded by  heavy  layers  of  a  hyaline  substance  that  is  stained  with  aniline 
blue  in  Mallory's  connective  tissue  stain.  The  cells  then  lie  in  cuboidal, 
rounded,  or  polygonal  chambers  completely  isolated  from  each  other  (Figs. 
112,  116).  Very  soon  the  cells  become  shriveled,  leaving  only  the  heavy 
walls  with  here  and  there  a  fragment  of  a  nucleus  or  of  cytoplasm. 

The  layer  of  parenchyma  immediately  surrounding  the  nerve  cord 
deserves  special  mention  on  account  of  its  peculiar  mode  of  development. 
In  early  stages,  when  the  nerve  cord  is  merely  a  thickening  in  the  hypoderm, 
this  layer  is  continuous  with  the  muscle  layer  lining  the  rest  of  the  hypo- 
derm  and  can  at  first  not  be  distinguished  from  that  layer  (Fig.  84) .  Even 
when  fully  developed  these  parenchyma  cells  are  narrow  and  very  much 


161]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  41 

elongated  and  in  that  respect  resemble  muscle  cells  (Fig.  102) .  These  cells 
are  themselves  covered  by  the  layer  of  mesenchyme  cells  that  later  lines 
the  muscles.  Ultimately,  however,  there  is  no  difference  between  the 
prenchyma  cells  that  originally  covered  the  nerve  cord  and  those  that  later 
migrated  over  them,  the  one  passing  gradually  into  the  other  (Fig.  106). 

At  times  the  intestine  becomes  separated  from  the  underlying  layer 
and  remains  attached  to  it  by  a  longitudinal  sheet  of  cells  of  single  thick- 
ness, the  ventral  mesentery.  The  intestine  adheres  to  a  broadened  surface 
of  the  terminal  cell,  but  its  outer  membrane  is  in  no  way  continuous  with 
the  covering  of  that  cell.  The  structures  by  which  the  egg  masses  appear 
to  be  suspended  in  the  older  females  are  not  mesenteries  but  the  remains 
of  the  ovaries  and  will  be  discussed  in  the  next  section. 

Reproductive  organs.  In  the  early  stages  one  can  find  no  difference 
between  males  and  females.  The  first  difference  appears  in  the  character 
of  the  diverticula  formed  at  the  posterior  end  of  the  intestine.  In  the  female 
three  diverticula  are  formed  (Fig.  109),  one  for  the  seminal  receptacle  and 
two  for  the  oviducts,  while  in  the  male  only  two  appear  for  the  sperm 
ducts  (Fig.  29).  These  diverticula  have  made  their  appearance  before  the 
28  day  stage  (Figs.  64,  65).  Somewhat  later  the  ovaries  become  differ- 
entiated from  the  testes  by  the  formation  of  buds  along  the  ventral  sides 
(Figs.  76,  84,  86).  These  buds  are  not  always  opposite  in  the  two  ovaries 
nor  are  they  of  uniform  size  (Fig.  62) . 

Each  ovary  at  first  is  enclosed  by  a  definite,  heavy  membrane,  but 
later  the  membrane  becomes  thin  at  the  buds  and  the  eggs  pass  into  the 
body  cavity  soon  after  they  have  begun  the  growth  period  (Figs.  76, 84, 86). 
The  eggs,  however  do  not  lie  loose  in  the  body  cavity,  but  continue  to  be 
enclosed  in  thinner  membranes  of  the  ovary.  By  the  time  the  first  eggs 
have  reached  their  full  size  nearly  all  of  the  germ  cells  have  left  the  ovarian 
tubes  and  have  in  masses,  strands,  or  sheets  become  distributed  among 
the  developed  oocytes  which  tend  to  form  layers  around  them.  As  the 
increase  in  the  diameter  of  the  body  continues,  the  ovarian  tubes  become 
broadened  dorso-ventrally,  and  by  the  discharge  of  the  germ  cells  they 
become  flattened,  so  that  they  take  the  form  of  broad,  thin  sheets  suspend- 
ed from  the  dorsal  muscles  (Fig.  79) .  In  later  stages  they  remain  as  double 
membranes  still  helping  to  support  the  masses  of  eggs  in  the  body  cavity. 
The  extensions  of  the  membranes  at  the  buds  have  become  thrown  into 
many  folds  and  have  been  thickened  in  places  to  help  in  the  support  of 
the  ovarian  mass.  At  the  time  of  the  discharge  of  the  eggs  the  membranes 
become  ruptured  and  the  heavy  parts  remain  attached  to  the  dorsal  muscles 
(Fig.  46). 

The  growth  period  in  the  oocytes  begins  somewhat  before  the  homo- 
geneous layer  is  formed  under  the  larval  cuticula  and  continues  until  the 
formation  of  the  adult  cuticula  is  well  under  way  (Figs.  76, 86, 77).    It  does 


42  ILUNOIS  BIOLOGICAL  MONOGRAPHS  1162 

not  occur  simultaneously  in  all  of  the  germ  cells  but  progresses  from  the 
buds  toward  the  dorsal  part  of  the  ovary.  The  full-grown  oocyte  is  about 
0.023  mm.  in  diameter  and  is  surrounded  by  a  definite  membrane.  At  the 
center  of  the  cell  is  found  a  large  nucleus,  while  the  cytoplasm  is  filled  with 
yolk  granules.  The  nucleus  has  a  diameter  of  about  0.006  mm.  and  consists 
of  a  large,  central  chromophil  mass  surrounded  consecutively  by  an  achro- 
matic and  a  chromatic  layer  (Fig.  106). 

Toward  the  anterior  end  the  ovaries  gradually  decrease  in  size,  the  space 
surrounding  them,  even  on  the  dorsal  side,  becoming  filled  with  parenchyma. 
In  some  cases  the  invading  parenchyma  interrupts  the  ovaries  at  places, 
forming  bead-like  masses  following  each  other  in  longitudinal  series.  The 
formation  of  these  masses  is  even  less  regular  than  the  location  of  the  buds 
on  the  ventral  sides  of  the  ovaries. 

At  the  posterior  end  the  oviducts  are  formed  by  continuations  of  the 
ovaries  and  they  unite  to  form  the  cloacal  gland  and  the  seminal  receptacle 
(Figs.  109-11).  It  has  been  impossible  in  the  very  early  stages  to 
recognize  the  germ  cells  in  this  region,  but  at  the  time  the  ovaries  are 
still  round  they  pass  without  interruption  back  to  the  point  of  union 
and  form  a  mass  of  cells,  the  rudiment  of  the  cloacal  gland,  around 
the  ventral  side  of  the  intestine.  At  that  stage  the  lateral  diverticula 
connect  with  these  cells  near  the  latero-posterior  margins  of  the  mass 
while  the  ventral  diverticulum  joins  them  somewhat  anterior  to  those 
points.  The  seminal  receptacle  exists  as  an  anterior  lobe  of  the  cell  mass. 
The  membrane  surrounding  those  structures  is  continuous  with  those  sur- 
rounding the  ovaries  and  no  difference  is  apparent  in  the  character  of  the 
cells  of  the  cloacal  structures  and  the  ovaries,  either  in  staining  reaction 
or  in  structure. 

Later  the  cells  become  modified  so  that  it  is  impossible  to  distinguish 
between  those  that  have  been  derived  from  the  intestine  and  those  derived 
from  the  germ  glands.  The  oviducts  become  indistinguishable  behind  the 
points  where  they  enter  the  cloacal  gland.  Anterior  to  those  points  the 
cells  in  the  oviducts  rearrange  themselves  so  as  to  form  definite  walls 
around  the  central  ducts  (Figs.  88-90,  93-95).  Even  at  that  stage  the 
change  from  oviducts  to  ovaries  is  a  gradual  one,  the  oviducal  walls 
continuing  farther  anteriad  on  the  ventral  side  than  on  the  dorsal. 

The  cloacal  gland  takes  up  a  median  position  beginning  somewhat 
posterior  to  the  points  at  which  the  ovaries  were  previously  inserted  into 
the  intestine  and  extending  anteriad  to  the  seminal  receptacle,  into  which  it 
opens  broadly  (Figs.  78,  93-95,  99, 100).  The  intestine  opens  into  the  dorsal 
side  of  the  gland  near  its  posterior  end,  the  oviducts  open  into  the  latero- 
ventral  sides  near  the  anterior  end.  The  cells  of  the'  gland  become  closely 
packed  and  form  finger-like  projections  that  extend  inward  and  forward 


163]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  43 

into  the  seminal  receptacle.  The  large  muscle  surrounding  the  posterior 
part  of  the  gland  has  been  described  under  the  topic  of  cloacal  musculature. 

The  seminal  receptacle  extends  forward  as  an  elongated  sac  with  defi- 
nite walls  similar  to  those  of  the  oviducts  at  their  posterior  ends.  It  is 
empty  and  distended,  occupying  in  cross  section  fully  one  half  the  diameter 
of  the  body  and  extending  lengthwise  over  a  space  equal  to  three  or  four 
times  that  diameter.  The  intestine  passes  around  to  the  ventral  side  of  the 
body  before  the  end  of  the  seminal  receptacle  has  been  reached. 

The  testes  in  the  males  remain  as  cylindrical  or  somewhat  triangular 
tubes  extending  nearly  the  whole  length  of  the  body  (Figs.  72,  80,  107,  108). 
They  are  enclosed  in  heavy  membranes  and  very  early  become  completely 
surrounded  by  parenchyma  cells.  As  in  the  ovaries  so  in  the  testes  there  are 
never  any  traces  of  cellular  walls. 

At  the  anterior  end  the  testes  are  subject  to  bead  formation  similar  to 
that  in  the  ovaries.  The  sperm  ducts  are  posterior  extensions  of  the  testes, 
opening  into  the  intestine  a  short  distance  anterior  to  the  anus,  and  in  the 
early  stages  in  no  way  distinguishable  from  the  testes  (Figs.  29,  70-71). 
Cellular  walls  for  the  sperm  ducts  are  formed  only  within  the  cloacal  mus- 
culature, anterior  to  that  all  of  the  cells  develop  into  spermatozoa. 
The  intestinal  diverticula  as  in  the  case  of  the  females  consist  of  nothing 
more  than  a  turning  out  of  the  walls  of  the  intestine  at  those  points. 

The  transformation  from  spermatocytes  to  spermatozoa  begins  at  a 
slightly  later  stage  in  development  than  does  the  growth  of  the  oocytes  in 
the  female.  It  takes  place  almost  simultaneously  in  all  parts  of  the  testes 
and  is  completed  before  the  adult  cuticula  has  been  fully  formed. 

The  chromatin  rod  appears  as  a  semicircle  at  one  side  of  a  rounded  cell, 
but  later  becomes  straightened  and  takes  up  a  median  position  while  the 
cell  becomes  spindle-shaped.  At  the  same  time  the  cytoplasmic  contents 
pass  to  one  end  leaving  the  rod  at  the  other  end  surrounded  by  only  a 
thin  layer  of  cytoplasm,  the  thickest  part  of  the  spindle  being  either  at  or 
even  beyond  the  end  of  the  rod  (Figs.  12, 13, 18, 19).  In  this  form  the  sper- 
matozoa leave  the  male.  Before  they  pass  into  the  body  of  the  female  they 
become  somewhat  elongated  (Fig.  10).  In  the  seminal  receptacle  of  the 
female  the  cytoplasmic  part  of  the  spermatozoon  elongates  into  a  heavy 
flagellum  of  uniform  diameter  while  the  rod  remains  as  a  slightly  thickened 
head  at  one  end  (Fig.  17). 


44  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [164 


OBSERVATIONS  ON  PARAGORDIUS  VARIUS 

On  account  of  the  excellent  description  of  the  adult  organization  of  this 
species  by  Montgomery  in  1903  and  on  account  of  the  general  similarity  in 
the  development  of  this  species  and  the  one  just  described,  the  following 
description  will  be  made  as  brief  as  possible. 

DETERMINATION  OF  THE  SPECIES 

Nothing  needs  to  be  added  to  the  descriptions  of  this  species  given  by 
Montgomery  (1898,  1903)  except  that  here  also,  as  in  Gordius  rohustus, 
there  are  present  two  longitudinal,  darker  bands;  a  broader  dorsal  and  a 
narrower  ventral  band.  They  are  even  more  distinct  than  in  the  previous 
species. 

HABITS  OF  THE  ADULTS 

This  species  prefers  quiet  water  to  rapids  and  more  frequently  inhabits 
lakes  than  streams.  It  is  not  very  abundant  in  the  waters  about  Urbana, 
but  is  the  common  species  reported  from  the  Great  Lakes  region.  Nothing 
has  been  observed  in  regard  to  the  winter  habitat.  The  earliest  specimens 
were  taken  near  Urbana  the  latter  part  of  May,  1914.  At  Douglas  Lake 
large  numbers  were  emerging  from  their  hosts  the  latter  part  of  June,  1915. 
While  at  Urbana  both  males  and  females  were  found  in  the  grass  at  the 
water's  edge,  only  males  were  found  in  similar  positions  at  Douglas  Lake. 
Females  that  had  emerged  during  the  night  could  still  be  found  swimming 
near  the  shore,  but  during  the  entire  summer  of  1915  only  a  few  females 
were  found  that  had  wound  themselves  around  grass  and  had  laid  eggs. 

Females  that  have  just  emerged,  while  swimming  near  the  shore,  soon 
encounter  males  and  copulation  takes  place.  The  deposition  of  eggs  begins 
the  following  day.  On  June  27,  1915,  an  adult  female  was  removed  from 
a  host.  It  was  kept  alone  in  an  aquarium  until  the  29th,  when  it  was  placed 
with  a  male  in  a  large  vial  and  mating  was  observed.  The  next  morning 
it  was  found  to  have  laid  a  string  of  eggs.  Another  female  removed  from 
the  host  on  June  30  and  mated  on  the  same  day  laid  eggs  July  1.  Other 
similar  cases  were  observed. 

Mating  was  observed  in  several  cases.  The  process  is  in  every  respect 
similar  to  that  described  for  Gordius  rohustus.  The  male  more  actively 
responds  to  the  stimulus  from  the  female  and  the  discharge  of  sperm  is  al- 
most instantaneous.  There  is  again  no  choice  of  direction  and  discharges 
of  sperm  may  in  some  cases  take  place  at  other  parts  of  the  body  of  the 
female  than  the  posterior  end.  There  is  no  interlocking  of  the  lobes  at  the 
posterior  ends  of  the  two  specimens,  and  after  copulation  the  spermatozoa 


1651  LIFE  HISTORY  OF  GORDIVS  AND  PARAGORDIUS—MA  Y  45 

remain  in  a  large  mass  enveloping  the  lobes  of  the  female,  but  pass  into  the 
seminal  receptacle  in  less  than  a  day. 

On  July  9  a  mutilated  male  was  obtained  from  the  lake.  It  consisted  of 
the  posterior  end  of  the  body  with  more  than  a  third  of  the  body  removed 
from  the  other  end.  A  female  was  placed  with  this  male  and  after  a  few 
hours  showed  a  mass  of  spermatozoa  at  the  posterior  end. 

The  eggs  are  deposited  in  long  strings  about  0.2  mm.  in  diameter,  and 
adhere  very  tenaciously  to  each  other.  Females  will  deposite  eggs  in 
aquaria  just  as  freely  as  in  nature.  When  grass  or  other  objects  are  present 
the  strings  are  wound  around  them,  otherwise  they  are  deposited  in  large, 
tangled  masses. 

Males  and  females  that  have  discharged  their  reproductive  products 
die  and  disintegrate  in  the  manner  described  for  the  previous  species. 

EARLY  DEVELOPMENT 

The  observations  made  on  the  development  and  structure  of  the  larva 
are,  for  reasons  stated  before,  only  fragmentary  and  can  not  be  included 
in  this  report. 

PARASITISM 

Like  Gordius  robustus,  this  species  enters  a  host  as  larva  and  undergoes 
its  entire  development  in  the  parasitic  stage. 

Hosts.  Both  at  Douglas  Lake  and  Urbana  parasitic  stages  were  found  in 
adults  or  older  nymphs  of  Gryllus  assimilis  (Fabricius)  as  defined  by  Rahn 
and  Hebard  (1915).  At  Douglas  Lake  they  were  also  found  in  Nemobius 
fasciqtus  (DeGeer).  The  specimen  staken  from  Nemobius  were  as  a  rule 
smaller  and  shorter  in  proportion  to  their  diameters  than  were  those  taken 
from  Gryllus. 

Altho  the  larvae  penetrate  the  tissues  of  various  species  of  aquatic 
animals  it  has  been  impossible  to  determine  if  any  or  all  of  these  animals 
may  serve  as  intermediate  hosts.  If  some  of  them  do  serve  as  intermediate 
hosts  they  must  serve  merely  as  carriers.  The  delicate  tissues  that  appear 
as  soon  as  the  larva  begins  to  change  into  the  parasitic  form  make  it  impos- 
sible for  a  further  change  of  hosts  to  take  place  without  causing  the  destruc- 
tion of  the  parasite.  Attempts  to  infect  the  hosts  artificially  proved 
unsuccessful. 

Infection.  Only  two  infected  hosts  were  taken  at  Urbana.  At  Douglas 
Lake  in  1915  adults  were  emerging  from  the  hosts  in  large  numbers  the  latter 
part  of  June  and  young  parasitic  stages  were  still  found  by  the  middle  of 
August.    Early  parasitic  stages  were  obtained  thruout  the  entire  summer. 

Infection  in  this  species  also  was  extremely  local  and  slightly  heavier  in 
females  than  in  males.  Of  125  males  of  Gordius  assimilis  collected  on  the 
hill  just  above  the  laboratory  and  within  half  a  mile  of  the  lake  6,  or  5  per- 
cent, were  infected,  yielding  7  parasites.  Of  152  females  collected  at  the 
same  place  24  were  infected,  making  an  infection  of  about  17  per  cent  and 


46  JLUNOIS  BIOLOGICAL  MONOGRAPHS  1166 

3deldmg  31  parasites.  In  collections  of  the  same  species  made  near  the 
shore  154  males  yielded  35  infected  specimens  or  an  infection  of  23  per  cent 
and  contained  52  parasites,  276  females  contained  135  infected  specimens 
or  an  infection  of  49  per  cent  and  yielded  377  parasites,  averaging  more 
than  two  parasites  to  each  infected  host.  During  the  latter  part  of  the 
summer  37  large  nymphs  were  collected  on  the  hill  about  two  miles  from 
the  lake  and  not  a  single  one  was  found  to  be  infected.  The  specimens  of 
Nemobius  fasciatus  were  all  collected  near  the  shore.  Of  15  males  8  were 
found  to  be  infected,  yielding  16  parasites,  and  of  24  females  only  6  were 
infected  containing  12  parasites. 

The  habits  of  this  host  also  make  an  intermediate  carrier  not  necessary. 
I  have  several  times  found  crickets  accumulated  in  large  numbers  about 
pools  of  water  at  night.  The  fact  that  many  unmated  females  of  Para- 
gordius  varius  were  found  in  the  shallow  water  of  the  lake  during  the  early 
forenoon,  but  disappeared  later,  indicates  that  infected  hosts  get  into  the 
water  and  lose  their  parasites  during  the  early  morning.  The  local  character 
of  the  infections  shows  that  infection  takes  place  at  or  near  the  water's 
edge. 

Location  in  the  host.  Early  developmental  stages  of  Paragordius  varius 
have  not  been  found  in  sections  of  hosts.  In  later  stages  the  parasites  lie 
free  in  the  body  cavity  (Fig.  134).  In  dissections  the  location  in  the  host 
is  found  to  be  in  every  respect  similar  to  that  of  Gordius  robustus. 

Practically  no  effect  of  the  parasite  on  the  host  was  found  except  in 
cases  of  very  hesivy  infection.  In  those  cases  a  diminution  in  the  size  of 
the  reproductive  organs  could  be  detected. 

Length  of  parasitic  period.  Since  experiments  were  unsuccessful ,  no  direct 
observations  on  the  developmental  period  could  be  made,  and  since 
infection  took  place  almost  uniformly  thruout  the  summer,  the  time  of 
infection  and  time  of  emergence  could  also  not  be  taken  as  criteria.  The 
earliest  appearance  of  adult  parasites  in  n\Tnphs,  however,  produced  some 
valuable  evidence  on  the  subject.  Most  of  the  nymphs  of  Gryllus  appeared 
during  the  last  week  in  June  and  Nemobius  did  not  hatch  until  about  a 
week  later.  By  the  middle  of  August  adult  parasites  were  found  in  the 
nymphs  of  both  species.  The  first  adult  Paragordius  varius  from  Nemobius 
fasciatus  was  obtained  on  August  14  while  the  host  was  still  a  n>Tnph. 
The  developmental  period  can  not  possibly  have  been  more  than  six  weeks. 
Some  of  the  first  infected  specimens  of  Nemobius  fasciatus  were  obtained 
on  August  2,  and  the  parasites  at  that  time  were  mostly  younger  than  the 
28  day  stage  in  Gordius  robustus.  On  August  12  most  of  the  parasites  were 
of  nearly  adult  size. 

Emergence  in  this  species  occurs  in  a  manner  similar  to  that  in  Gordius 
robustus.  About  six  specimens  were  seen  leaving  their  hosts.  In  all  cases 
the  parasites  emerged  with  the  anterior  end  first  from  near  the  anus  of  the 


167]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  47 

host.  The  definite  reaction  toward  the  presence  of  water  was  again  observ- 
ed. On  July  12  a  male  of  Gryllus  assimilis  was  found  to  have  the  anterior 
end  of  a  female  of  Paragordius  varius  protruding  from  the  posterior  end 
when  it  was  caught.  The  cricket  was  placed  in  a  dry  vial  and  the  parasite 
withdrew  and  remained  in  the  host  until  the  latter  was  placed  in  water 
in  the  laboratory  two  hours  later.  In  the  water  the  parasite  left  the  host 
in  less  than  five  minutes.  The  emergence  was  witnessed  by  Dr.  W.  W. 
Cort  and  Mr.  A.  C.  Conger.  Other  similar  cases  were  observed  during  the 
summer. 

ORGANOGENY 

On  account  of  the  lack  of  material  in  the  early  stages  little  can  be  said 
about  the  metamorphosis  and  derivation  of  tissues  in  this  species.  Only 
two  young  specimens  were  obtained  and  they  were  mounted  as  totos 
(Figs.  130,  131). 

Cuticula.  Stages  in  its  development  in  this  species  are  even  more 
difficult  to  obtain  than  in  Gordius  robusius  indicating  that  the  cuticula 
develops  with  extreme  rapidity. 

Larval  cuticula.  It  was  in  this  species  that  the  shedding  of  the 
larval  cuticula  was  first  observed.  Nevertheless,  its  presence  is  difficult 
to  demonstrate  during  the  development  of  the  adult  cuticula.  It  is  clearly 
evident  in  younger  stages  and  changes  in  size  and  thickness  during  develop- 
ment just  as  does  that  of  the  previous  species.  But  no  homogeneous  layer 
appears  under  it  before  the  beginning  of  the  development  of  the  adult 
cuticula.  Much  later,  when  the  fibrous  cuticula  has  almost  reached  its 
full  development,  a  very  thin,  homogeneous  layer  appears  under  the  larval 
cuticula  (Fig.  167)  but  is  difficult  to  distinguish  because  it  adheres  closely 
and  has  nearly  the  same  density  and  staining  reactions.  The  larval  cuticula 
later  separates  from  this  layer  (Fig.  ^163)  and  comes  off  in  large  sheets, 
being  retained  longest  at  the  ends.  Adult  specimens  removed  from  their 
hosts  frequently  show  these  pieces  of  the  larval  cuticula  trailing  from  the 
two  ends.  When  such  sheets  of  larval  cuticula  are  mounted  and  stained 
they  show  a  perfectly  homogeneous  structure. 

Adult  cuticula.  The  development  of  the  adult  cuticula  commences  with 
the  formation  of  a  rather  indefinite  granular  layer  under  the  larval  cuticula, 
but  almost  simultaneously  there  appears  under  this  a  lighter  layer  which 
is  the  beginning  of  the  fibrous  cuticula.  The  granular  layer  is  the  rudiment 
of  the  homogeneous  or  non-fibrous  cuticula  and  areolar  structures  of 
the  adult.  Fibrous  cuticula  and  areolar  structures  develop  simultaneously 
(Figs.  161,  169).  The  stains  employed  failed  to  bring  out  any  structures 
in  the  fibrous  cuticula  during  its  development.  The  hypoderm  cells 
often  give  off  conical  projections  into  the  developing  cuticula  and  the 
apices  of  the  cones  can  sometimes  be  seen  to  extend  to  the  granular 
layer  (Figs.  166, 167).    At  the  points  where  the  apices  reach  the  granular 


48  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [168 

layer  the  latter  becomes  thickened  and  in  it  are  developed  hyaline 
bodies,  usually  two  at  each  point  (Figs.  104,  161,  169).  These  hyaline 
bodies  later  become  oval  in  outline  and  give  the  cuticula  its  areo- 
lated  appearance  (Fig.  160).  The  homogeneous  cuticula,  which  always 
remains  more  or  less  granular,  is  formed  from  the  granular  layer  chiefly 
over  these  bodies,  but  also  between  and  under  them.  The  connections 
between  the  granular  layer  and  the  hypoderm  remain  as  definite  proto- 
plasmic strands,  coming  to  the  surface  usually  between  the  oval  bodies 
(Figs.  1,  160,  164).  At  intervals  heavier  protoplasmic  strands  pierce 
the  fibrous  cuticula,  and  over  them  the  granular  layer  thickens  to  form 
the  short  cuticular  tubercles  or  bristles  which  are  found  especially  in 
two  ventral  rows,  but  also  sparingly  scattered  over  the  rest  of  the  body 
(Figs.  140,  164).  Where  the  heavier  strands  pass  thru  the  cuticula  the 
fibers  remain  separated  to  form  a  cross  (Fig.  1).  At  the  sides  of  the  male 
cloacal  aperture  the  bristles  in  the  two  ventral  rows  are  very  much  elonga- 
ted. Anteriad  from  that  point  they  gradually  shorten,  posteriad  they 
remain  high  to  the  bases  of  the  prongs  and  then  become  shorter  and  are 
scattered  over  the  inner  ventral  surfaces  of  the  prongs  (Fig.  133).  The 
oval  bodies  are  absent  on  these  surfaces. 

The  outer  surface  of  the  homogeneous  or  non-fibrous  cuticula  is  usually 
hyaline  in  appearance,  while  the  granules  remain  evident  in  a  lower  layer 
which  indefinitely  grades  into  the  hyaline  layer,  and  at  places  may  be 
absent  or  at  others  may  reach  the  surface.  The  bristles  are  composed 
chiefly  of  the  hyaline  substance,  but  usually  show  at  the  base  a  cone  of  the 
granular  material.  Since  the  granular  substance  stains  deeply  it  has  been 
impossible  to  trace  the  protoplasmic  strands  farther  than  to  the  bases  of 
the  bristles. 

Fibers  do  not  appear  in  the  cuticula  until  it  has  reached  nearly 
its  full  diameter.  They  are  wound  spirally  around  the  body  in  two 
directions  so  that  they  cross  each  other  forming  antero-posterior  angles  of 
about  175  degrees  and  lateral  angles  of  about  65  degrees  (Fig.  1).  Since 
the  fibers  are  all  of  the  same  size  and  the  layers  alternate  regularly,  cross 
sections  of  the  cuticula  do  not  present  the  appearance  of  stratification  so 
obvious  in  the  cuticula  of  Gordius  robustus  unless  the  sections  are  made 
nearly  parallel  to  one  set  of  fibres.  The  number  of  layers  of  fibers  is  vari- 
able, but  seldom  exceeds  24.  Montgomery  reports  only  11,  but  his  figures 
show  that  he  made  his  counts  on  sections  parallel  to  one  series,  and  counted 
only  alternate  layers.  Over  the  white  surface  at  the  anterior  end  the  fibers 
become  more  closely  packed  and  tend  to  form  a  homogeneous  mass. 

The  color  appears  in  the  manner  described  for  Gordius  robustus  and 
reaches  its  full  intensity  before  the  parasite  leaves  its  host.  On  June  30  a 
female  was  removed  from  the  host  when  it  was  still  incompletely  colored. 
The  dark  ring  and  the  dorsal  and  ventral  bands  were  clearly  outlined. 


169]  LIFE  HISTORY  OP  GORDIUS  AND  PARAGORDIUS—MA  7  49 

color  had  begun  to  appear  over  the  rest  of  the  cuticula  at  the  two  ends, 
but  the  middle  region  of  the  body  was  still  white.  The  specimen  was  kept 
alive  until  July  26,  when  it  was  attacked  by  fungi  and  had  to  be  killed. 
It  had  been  mated  and  had  laid  some  eggs,  and  had  been  kept  in  an  open 
glass  dish  in  the  window  where  the  sun  shone  on  it  part  of  the  day;  but  the 
color  had  not  noticeably  changed  except  that  the  white  had  become  soiled. 

Hypoderm.  The  hypoderm  in  this  species  develops  very  much  as  in  Gordius 
rohustus.  The  cells  at  first  are  flattened,  very  early  become  columnar,  and 
after  the  completion  of  the  adult  cuticula  become  flattened  again  over 
most  of  the  surface  of  the  body.  They  remain  higher  at  the  two  ends.  At 
the  anterior  end,  under  the  white  surface,  they  project  far  into  the  interior, 
becoming  rod-shaped  or  almost  fibrous  in  nature.  The  nuclei  remain  in 
the  outer  halves  of  the  cells  while  the  lower  parts  become  clear  and  form  a 
distinct  mass  just  anterior  to  the  supraesophageal  ganglion.  These  hyaline 
bases  of  the  cells  later  disintegrate  or  else  form  a  substance  that  is  dissolved 
during  the  preparation  of  the  mount  (Figs.  153,  154). 

Protoplasmic  connections  between  the  hypoderm  cells  are  present  in 
this  species  as  in  the  previous  one  but  no  canal  system  has  been  found. 
The  cells  are  in  cross  section  more  easily  distinguishable  than  in  Gordius 
robustus. 

The  nuclei  from  the  first  are  more  distinct  than  in  Gordius  robustus 
and  each  consists  of  a  large  central  nucleolus  surrounded  by  an  achromatic 
sphere  and  a  somewhat  indefinite  membrane  (Figs.  165,170).  Later  the 
membranes  become  more  distinct,  but  the  nuclei  do  not  become  so  definite- 
ly outlined  as  in  Gordius  robustus  and  the  fusion  of  chromatic  spheres 
occurs  only  in  very  few  instances.  During  the  formationof  the  adult 
cuticula  the  chromatic  substance  increases  in  quantity  and  becomes  scat- 
tered thruout  the  nucleus  (Fig.  167).  In  the  adult  stage  the  nucleus 
shrinks  and  the  chromatic  substance  forms  one  or  two  discs,  almost  com- 
pletely filling  the  membrane. 

Nervous  system  This  system  is  built  on  the  same  fundamental  principle 
as  in  the  previous  species,  but  while  some  parts  stand  out  clearer,  the  struc 
ture  of  the  others  is  not  so  easily  brought  out. 

Central  nervous  system.  The  brain  in  this  species  also  appears  in 
the  posterior  part  of  the  proboscis,  but  does  not  begin  its  development 
until  even  later  than  in  Gordius  robustus.  The  rudiment  of  the  brain 
appears  as  a  group  of  deeper  staining  cells  around  the  connecting  strand 
between  the  stylets  and  the  base  of  the  proboscis  (Fig.  162)  but  the 
cells  soon  lose  their  staining  properties  and  become  indistinguishable  from 
the  mesoderm  cells  which  surround  them  (Fig.  151).  The  bundles  of 
nerve  fibres  leading  from  them  can,  however,  be  distinguished.  Even  at 
a  much  later  stage,  when  the  nerve  cord  is  beginning  to  separate  from 
the  hypoderm,  the  gangHon  cells  are  difficult  to  distinguish  from  the  rest. 


so  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [170 

At  that  time  the  main  group  lies  in  an  indefinite  mass  over  the  esophagus, 
just  anterior  to  the  end  of  the  nerve  cord,  and  is  connected  with  the  cord 
by  two  large  commissures  passing  around  the  esophagus.  Under  the  eso- 
phagus, at  the  very  end  of  the  cord,  a  smaller  group  of  ganglion  cells  is 
more  easily  distinguishable. 

In  further  development  the  dorsal  group  becomes  completely  isolated 
from  other  tissues,  remaining  connected  only  with  the  nerve  cord  by  the 
commissures  and  in  some  cases  also  with  the  anterior  hypoderm  by  scatter- 
ed, half  disintegrated  fibres  (Fig.  153).  No  marked  change  occurs  in  the 
ventral  group.  At  the  sides  of  this  group  fibres  pass  anteriad  to  the  anterior 
hypoderm  cells.  The  fibres  usually  become  more  or  less  definitely  separated 
into  two  ventral  and  two  lateral  tracts. 

The  ventral  cord  arises  and  develops  as  described  for  Gordius  robustus 
(Figs.  135,  146,  147,  158).  The  cellular  elements  do  not  all  remain  under 
the  fibre  tracts,  pushing  up  into  them  as  they  did  in  Gordius  robustus,  but 
grow  up  over  the  sides,  partly  enclosing  the  fibres  and  leaving  them  in 
contact  with  the  parenchyma  over  only  about  one  third  of  the  circum- 
ference, in  later  stages  even  less  (Fig.  141).  On  account  of  this  over- 
growth of  the  cells  the  cross  fibres  do  not  present  a  radiating  appearance 
but  cross  each  other  at  various  angles  within  the  cord.  There  are,  how 
ever,  two  longitudinal  rows  of  heavier  fibres  originating  from  the  two 
primary  cell  rows  and  passing  to  the  dorsal  side  of  the  cord,  dividing  the 
longitudinal  fibres  into  three  main  tracts  (Fig.  159). 

The  structure  of  the  large  cells  in  the  two  primary  rows  is  more  easily 
demonstrated  in  this  species  than  in  the  previous  one.  The  cells  are  bipolar, 
giving  off  one  fibre  to  the  dorsal  wall  of  the  cord  and  another  to  the  longi- 
tudinal fibre  tract  (Fig.  139).  The  body  of  the  cell  is  rounded  or  flask- 
shaped  and  the  two  fibres  are  given  off  at  one  side.  Some  smaller  cells 
were  also  found  to  be  bipolar  and  of  similar  structure,  but  in  case  of  the 
majority  of  the  smaller  cells  it  is  impossible  to  make  out  the  exact  structure. 

No  cell  bodies  can  be  distinguished  in  the  connection  between  the  nerve 
cord  and  hypoderm  after  the  two  have  separated,  but  fibres  can  be  traced 
thru  it  from  the  cord  to  the  hypoderm.  At  the  point  where  the  fibres  from 
the  cord  enter  the  hypoderm  longitudinal  fibres  are  frequently  found,  and 
these  fibres  in  some  cases  separate  to  form  a  longitudinal  canal,  the  sub- 
neural  canal  of  European  workers. 

In  the  male  the  nerve  cord  ends  at  the  posterior  end  as  it  does  in  the 
previous  species.  The  cloacal  ganglion  consists  of  a  slight  thickening  of 
the  cord  beginning  somewhat  anterior  to  the  musculature  of  the  sperm 
ducts  and  extending  back  to  the  point  of  bifurcation  of  the  cord  (Fig.  164). 
It  is  intimately  connected  with  the  musculature  of  the  vasa  deferentia. 

The  cloacal  ganglion  in  the  female  is  similar  to  that  found  in  Gordius 
robustus  but  presents  some  modifications  on  account  of  the  posterior  exten- 


171]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  51 

sion  of  the  dorsal  and  lateral  lobes.  The  nerve  cord  ends  at  the  beginning 
of  the  lateral  lobes  and  is  partly  inturned  with  the  hypoderm  that  lines 
the  cloaca.  On  account  of  this  inturning  the  cord  passes  into  the  hypoderm 
not  on  the  external  body  surface  as  it  does  in  Gordius  robustus,  but  in  the 
ventral  wall  of  the  cloaca.  Here  the  longitudinal  fibers  pass  into  the  hypo- 
derm and  to  a  less  extent  than  in  the  previous  species  they  also  pass  around 
to  the  dorsal  side  of  the  cloaca. 

Peripheral  nervous  system.  Just  as  in  the  previous  species  the  peri- 
pheral nervous  system  consists  of  fibers  and  cells  in  the  hypoderm.  Since 
these  structures  were  clearly  described  by  Montgomery,  no  detailed 
account  of  them  will  be  given  here. 

Digestive  system.  This  system  is  like  that  found  in  Gordius  robustus,  but 
in  the  adult  condition  does  open  to  the  exterior  at  the  anterior  end. 

Mouth  and  esophagus.  In  this  species  the  strand  of  cells  which  connects 
the  stylets  to  the  base  of  the  proboscis  remains  attached  to  the  anterior  end 
of  the  intestine  and  is  not  only  retained  in  the  tissue,  but  actually  undergoes 
development.  At  first  it  is  a  very  short  connection  between  the  part  of  the 
proboscis  that  does  not  develop  and  the  anterior  end  of  the  intestine,  but 
as  development  proceeds  it  elongates  and  thickens,  forming  a  bulb-like 
enlargement  in  front  of  the  intestine  with  an  elongation  projecting  dorsally 
over  the  end  of  the  latter  (Figs.  151,  153-4).  It  passes  thru  between  the 
dorsal  and  ventral  cell  groups  of  the  cephalic  ganglion  and  between  the 
two  commissures.  In  the  young  stages  it  has  been  impossible  to  demon- 
strate definitely  the  presence  of  a  tube  in  this  strand.  Altho  some  sections 
give  the  appearance  of  the  presence  of  a  capillary  tube,  this  tube,  if  present, 
is  so  small  and  its  walls  so  indefinite  that  it  cannot  be  traced.  At  about 
the  time  the  adult  cuticula  is  formed  most  of  the  cells  composing  the  strand 
disintegrate,  forming  a  tube  about  which  the  parenchyma  cells  form  fairly 
definite  walls.  Some  of  the  outer  cells  of  the  strand  usually  also  remain 
intact  and  take  part  in  the  formation  of  the  walls  (Figs.  153-4).  By  the 
loss  of  the  proboscis,  when  the  larval  cuticula  is  shed,  the  tube  is  opened 
at  its  anterior  end. 

Intestine.  The  development  of  the  intestine  proceeds  in  this  species  much 
as  it  does  in  Gordius  robustus.  Here  also  diverticula  are  formed  to  receive 
the  oviducts  and  sperm  ducts  (Figs.  148,  165).  The  cells  of  the  intestinal 
walls  are  more  easily  distinguished  than  they  were  in  the  previous  species, 
and  an  inner,  vascular  zone  is  never  differentiated.  The  modifications 
at  the  posterior  end  will  be  taken  up  in  the  discussion  of  the  reproductive 
system. 

Excretory  system.  This  species  also  presents  no  trace  of  an  excretory 
system 

Circulatory  system.  No  vessels  are  present,  but  longitudinal  cavities  are 
present  in  this  species  as  they  were  in  Gordius  robustus.    Here  also  the  main 


52  JLLimiS  BIOLOGICAL  MONOGRAPHS  [172 

cavity  lies  around  the  dorsal  part  of  the  intestine  and  may  be  divided  by 
the  gonads  into  a  median  canal  over  the  intestine  and  two  lateral  canals, 
or  the  median  canal  may  be  absent  (Figs.  145,  158).  In  the  males 
frequently  the  parenchyma  fills  the  entire  space,  leaving  no  cavities  around 
the  intestine.  In  the  females  there  is  usually  also  a  cavity  on  the  dorsal 
side  between  the  ovaries.  This  is  seldom  present  in  the  males.  In  later 
stages,  when  part  or  all  of  the  reproductive  products  have  been  discharged, 
other  cavities  appear  in  both  males  and  females. 

Muscles,  hs,  in  the  previous  species,  these  consist  of  a  cylinder  of 
longitudinal  fibers  just  beneath  the  hypoderm  and  of  the  cloacal  muscula- 
tures. The  cylinder  of  longitudinal  muscles  is  interrupted  only  on  the 
ventral  side  by  the  connection  between  the  nerve  cord  and  the  hypoderm, 
and  is  lost  in  the  parenchyma  before  the  extreme  ends  of  the  body  are 
reached. 

Longitudinal  muscles.  The  longitudinal  muscles  begin  their  differ- 
entiation slightly  later  than  they  do  in  Gordius  robustus.  In  the  youngest 
specimens  sectioned  they  are  still  similar  to  mesenchyma  cells,  and  appear 
rounded  or  cuboidal  in  cross  section,  but  have  the  shape  of  short  spindles 
when  viewed  from  the  side  (Figs.  147, 155, 156, 165).  Later  the  ends  elongate, 
and  the  main  bodies  of  the  cells  become  crowded  inward  by  the  intercala- 
tion of  the  elongating  ends  near  the  hypoderm.  Soon,  however,  the  bodies 
of  the  cells  also  elongate  and  the  diameters  become  nearly  equal  at  the 
inner  and  the  outer  edges.  The  ultimate  shape  of  the  muscle  cell  is  essen- 
tially the  same  as  in  the  previous  species,  but  the  cell  is  even  more  elong- 
ated and  the  nucleus  is  very  much  elongated  so  that  it  extends  even  into  the 
narrower  parts  of  the  cell  (Figs.  6,  158,  174).  The  adult  muscle  cell  shows 
a  layer  of  longitudinal  fibrils,  similar  to  that  of  the  previous  species,  lying 
just  inside  the  cell  membrane  and  completely  surrounding  the  remainder 
of  the  cell.  Some  of  the  cells  that  are  crowded  inward  by  the  nerve  cord 
and  come  to  lie  at  the  side  of  the  connecting  lamella  develop  into  muscle 
cells,  so  that  some  of  the  muscles  appear  to  be  inserted  on  the  lamella. 

Cloacal  musculature.  The  radiating  cloacal  musculature  of  the  male, 
so  prominent  in  the  previous  species,  is  lacking  in  Paragordius  varius 
except  for  a  few  longitudinal  fibres  at  the  posterior  side  of  the  cloaca 
which  are  clearly  continuous  with  the  longitudinal  body  muscles. 

The  circular  muscles  around  the  sperm  ducts  are  located  a  short  dis- 
tance anterior  to  the  cloaca  and  are  more  highly  developed  than  in  the 
previous  species  (Fig.  164).  They  develop  from  mesenchyme  cells  (Fig.  142). 

As  in  the  female  of  Gordius  robustus,  so  in  the  female  of  Paragordius 
varius,  circular  fibers  are  found  chiefly  around  the  duct  connecting  the  cloacal 
gland  with  the  seminal  receptacle,  but  also  surrounding  the  gland  itself 
and  in  a  thin  sheet  even  surrounding  the  cloaca  behind  the  gland.  Very 
thin  layers  of  these  fibers  also  surround  the  oviducts.    The  fibers  develop 


173]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  53 

from  mesenchyme  and  in  the  later  stages  have  heavy  walls  similar  to  those 
of  the  parenchyma. 

Parenchyma  and  mesenteries.  The  parenchyma  arises  as  in  the  preceding 
species,  but  fills  the  body  cavity  more  completely  in  the  early  stages.  It 
not  only  forms  the  lining  for  the  muscles  and  surrounds  the  testes  in  the 
males,  but  it  also  surrounds  the  ovaries  in  the  females.  As  the  ventral 
buds  in  the  ovaries  appear  and  the  eggs  fill  the  body  cavity,  the  inner  walls 
of  the  ovaries  become  extended  around  the  intestine  to  the  sides  of  the 
nerve  cord,  and  in  that  way  the  two  mesenteries  are  formed  (Fig.  158). 
The  outer  walls  of  the  ovaries  are  turned  back  upon  themselves  at  the 
points  where  the  buds  arise,  and  thus  double  lamellae  are  established  reach- 
ing from  those  points  to  the  muscles  on  the  dorsal  side  of  the  body.  There 
the  layer  of  each  lamella  that  lies  next  to  the  original  ovarian  tube  is  con- 
tinuous over  that  tube  with  its  inner  wall,  while  the  outer  layer  of  the 
lamella  is  continuous  with  the  outer  covering  of  the  ovarian  bud,  passing 
close  to  the  lining  of  the  muscles,  around  to  the  ventral  side  to  join  the 
ventral  edge  of  the  mesentery,  or  inner  wall  of  the  bud.  As  development 
proceeds,  the  germ  cells  leave  the  primary  ovarian  tubes,  just  as  they  do 
in  Gordius  rohustus,  and  the  outer  walls  of  these  tubes  appear  as  parts  of 
the  mesenteries.  As  a  result  the  mesenteries  in  later  stages  appear  to  be 
composed  of  three  layers  of  cells  in  the  dorsal  part  of  the  body,  but  of  a 
single  layer  in  the  ventral  part  (Fig.  159).  Even  in  the  males  the  paren- 
chyma forms  about  the  gonads  more  definite  layers  than  were  found  in 
Gordius  rohustus  (Fig.  174). 

During  the  formation  of  the  adult  cuticula  heavy  walls  appear  about 
the  parenchyma  cells,  in  many  cases  much  heavier  than  in  the  previous 
species  (Fig.  164).  The  cells  are  normally  somewhat  elongated,  poly- 
hedral or  barrel-shaped  (Figs.  3,  164),  but  may  in  other  cases  have  the 
irregular  polyhedral  form  found  in  Gordius  rohustus.  The  cells  in  this 
species  remain  more  intact  and  more  completely  fill  the  spaces. 

In  the  anterior  end,  behind  the  dorsal  group  of  ganglion  cells,  the  mesen- 
chyme cells  become  crowded  together  very  closely  and  form  a  capsule 
which  encloses  the  ganglion  cells  on  all  sides  except  that  covered  by  the 
flattened  anterior  surface  (Figs.  153-^).  This  capsule  is  formed  just  before 
the  heavy  cell  walls  appear.  Its  adult  structure  has  been  adequately 
described  by  Montgomery. 

Reproductive  organs.  The  germ  cells  arise  as  in  Gordius  rohustus,  and  in 
early  stages  can  not  be  distinguished  from  mesenchyme  cells  in  other  parts 
of  the  body  (Fig.  136).  In  the  middle  of  the  body  the  gonads  assume  a 
definite  shape  before  they  become  surrounded  by  mesenchyme  cells,  which 
at  that  time  have  become  easily  distinguishable  (Figs.  147, 156, 157).  After 
that  the  mesenchyme  proliferates  very  rapidly  and  completely  envelopes  the 
gonads  with  definite  layers.  The  gonads  of  the  two  sexes  can  not  be  dis- 
tinguished in  the  early  stages. 


54  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [174 

Development  of  the  testes  in  the  male  proceeds  as  described  for  Gordius 
robustus.  The  membranes  enclosing  the  testes  are  usually  not  so  heavy  as 
in  that  species  and  the  cellular  parts  of  the  sperm  ducts  extend  both  anterior 
and  posterior  to  the  short  muscular  areas. 

The  spermatozoa  develop  as  in  the  previous  species  except  that  the 
head  and  cytoplasmic  parts  become  more  definitely  separated  before  the 
axis  of  the  cell  becomes  straightened,  causing  the  spermatozoon  to  be 
doubled  upon  itself  when  it  is  first  formed  (Fig.  137).  Head  and  cytoplas- 
mic part  are  definitely  separated  from  each  other.  In  the  seminal  receptacle 
of  the  female  the  cytoplasm  elongates  into  the  heavy  flagellum  of  uniform 
diameter  (Fig.  138). 

,  The  reproductive  organs  in  the  female  develop  very  much  as  they  do  in 
Gordius  robustus.  The  membranes  forming  the  primary  ovarian  tubes  are 
not  so  heavy  as  in  that  species.  The  cloacal  structures  arise  essentially  as 
in  Gordius  robustus,  but  show  modifications  in  certain  details. 

The  part  of  the  cloaca  lined  by  the  invaginated  hjrpoderm  forms  a  tube 
at  the  posterior  end  of  the  body  equal  in  length  to  at  least  twenty  times 
the  diameter  of  the  body  at  that  point.  The  intestinal  diverticula  arise 
a  short  distance  anterior  to  the  point  of  union  between  ectoderm  and 
entoderm  and  are  less  distinct  than  in  Gordius  robustus,  appearing  only 
as  the  points  at  which  the  intestinal  wall  begins  to  become  modified. 
The  oviducts  develop  from  the  posterior  ends  of  the  primary  ovarian  tubes 
and  unite  to  form  the  rudiment  of  the  cloacal  gland  and  seminal  receptacle 
The  receptaculum  seminis  becomes  distinctly  separated  from  the  gland, 
remaining  connected  by  a  narrow  neck  (Fig.  168).  The  ovaries  open  at 
the  sides  into  the  anterior  end  of  the  gland  and  the  intestine  opens  into  it 
on  the  dorsal  side  at  the  posterior  end,  or  perhaps  it  would  be  more  correct 
to  say  in  this  case  that  the  gland  opens  into  the  ventral  side  of  the  intestine. 
(Figs.  168,  171). 

At  the  point  of  union  between  entoderm  and  ectoderm  a  constriction 
or  valve  appears  in  later  stages  (Fig.  171).  The  inner  ends  of  the  cells 
lining  the  cloaca  between  the  valve  and  the  cloacal  gland  secrete  a 
clear  substance  that  almost  completely  fills  the  lumen  of  the  tube. 
A  similar  substance  is  secreted  by  the  cells  lining  the  oviducts.  Radiating 
from  the  cells  are  thin  membranes  apparently  enclosing  the  substance, 
and  a  heavier  layer  surrounds  the  remnant  of  the  lumen.  In  the  adult 
stage  the  inner  part  of  the  secretion  is  swept  away  and  little  remains 
except  the  bases  of  the  membranes  which  Montgomery  regarded  as  cilia. 
The  hypoderm  of  the  posterior  region  of  the  cloaca  also  secretes  a  hyaline 
substance  which  passes  in  long  threads  thru  cuticular  pores  into  the  lumen 
(Figs.  7,  171).  This  substance  disappears  at  the  time  of  the  entrance 
of  the  spermatozoa  and  may  aid  in  their  migration  into  the  seminal  recep- 
tacle, but  the  secretion  of  the  substance  continues  after  insemination. 


1751  UPE  HISTORY  OF  GORDIUS  AND  PARAGORDI US— MA  Y  55 

The  epithelium  of  the  cloacal  gland  at  the  time  of  the  formation  of  the 
adult  cuticula  develops  projections  in  which  the  cells  appear  like  buds  on 
central  stalks.  (Fig.  163.) 

In  specimens  that  have  deposited  their  eggs  the  cells  become  shriveled 
and  the  body  cavity  contains  only  the  nerve  cord,  a  very  small  intestine, 
and  the  parenchyma  membranes,  which  now  have  all  taken  more  or  less 
a  dorso-ventral  position  and  tend  to  flatten  the  body  in  that  direction 
(Fig.  103). 


56  ILUNOIS  BIOLOGICAL  MONOGRAPHS  fl76 


DISCUSSION 

In  the  following  discussion  I  shall  compare  briefly  the  results  obtained 
in  the  present  investigations  with  those  obtained  by  other  authors  and  give 
interpretations  of  some  of  the  facts  observed.  In  the  comparisons  I  shall 
confine  myself  almost  exclusively  to  the  more  recent  literature.  The  lack 
of  proper  methods  of  investigation  makes  the  reports  of  the  older  writers 
of  little  value  except  as  historical  documents. 

BIOLOGY 

Altho  the  behavior  of  the  Gordiacea  has  attracted  the  attention  of  all 
workers  who  have  obtained  living  material,  the  observations  have  for  the 
most  part  been  fragmentary  and  have  yielded  little  that  is  of  scientific 
value.  Even  the  present  report  does  not  pretend  to  be  more  than  the  mere 
beginning  of  a*  systematic  study  of  the  behavior  of  certain  species  during 
the  different  stages  of  their  life  cycle. 

Occurrence  and  behavior  of  adults 

Various  workers  have  reported  that  among  the  Gordiacea  there  is  a 
predominance  of  males  over  females.  The  most  recent  statement  to  that 
effect  was  made  by  Meyer  (1913),  who  reported  that  he  collected  201 
specimens  and  found  only  6  to  be  females.  Von  Linstow  (1891)  found 
that  the  proportion  of  males  to  females  was  7:3.  More  recently  Miihldorf 
(1914)  stated  that  in  his  collections,  which  were  perhaps  larger  than  any 
previous  collections  made,  he  failed  to  find  any  consistent  difference  in  the 
number  of  males  and  females. 

With  the  additional  information  presented  in  this  paper  it  is  possible 
to  explain  the  previous  observations  and  to  show  that  the  differences 
observed  were  apparent  and  not  real. 

Von  Linstow  gives  a  table  of  the  specimens  collected  by  him,  including 
both  free  living  and  parasitic  forms.  His  conclusion  is  based  on  the  entire 
collection  which  included  31  females  and  74  males,  and  does  not  hold  true 
either  for  the  free  living  forms  or  the  parasitic  forms  when  considered 
separately.  In  case  of  the  parasitic  forms  he  actually  found  three  males 
and  five  females,  or  a  predominance  of  females. 

Camerano  in  the  following  year  published  several  tables  showing  the 
parasites  obtained  from  Blaps  mucronata  in  the  neighborhood  of  Turin. 
These  tables  show  that  he  also  found  no  predominance  of  males  over 
females. 

In  the  parasitic  forms  obtained  during  the  present  investigations  I  have 
been  unable  to  find  any  difference  in  the  number  of  specimens  of  the  two 
sexes. 


177]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  57 

So  far  as  the  parasitic  forms  are  concerned,  then,  there  is  in  literature 
no  evidence  of  any  real  difference  in  the  number  of  males  and  females  pro- 
duced. It  is  merely  necessary  to  explain  the  difference  observed  in  case  of 
free  living  specimens. 

The  results  of  Muhldorf  have  already  been  mentioned.  In  the  collec- 
tions of  Gordius  robustus  made  during  these  investigations  I  have  usually 
obtained  a  slight  predominance  of  females  over  males,  only  in  a  few  small 
collections  was  a  predominance  of  males  present.  In  the  collection  of 
Paragordius  varius  made  at  Urbana  the  females  were  far  more  numerous 
than  the  males.  At  Douglas  Lake,  however,  the  reverse  was  true.  Most 
of  the  collections  made  along  the  shore  of  the  lake  contained  very  few 
females. 

The  explanation  must  be  sought  in  the  behavior  of  the  animals  and  not 
in  any  real  difference  in  the  numbers  of  the  two  sexes.  The  specimens  in 
the  older  collections  were  obtained  mostly  accidentally  and  were  either 
specimens  that  had  just  left  their  hosts,  or  were  in  the  act  of  migration,  or 
specimens  that  had  not  found  a  normal  resting  place.  Since  males  are  as  a 
rule  more  active  than  females  and  more  seldom  come  to  rest  in  secluded 
places,  as  do  females  during  the  egg-laying  period,  it  is  but  natural  that 
they  were  the  ones  most  commonly  obtained  in  random  collections.  The 
results  of  Meyer  are  easily  explained  on  this  basis  as  he  obtained  his  speci- 
mens by  collecting  in  open  water  or  dredging  at  the  bottom  of  ponds.  In 
those  locations  he  would  get  nothing  but  migrating  specimens,  chiefly 
males.  Muhldorf  made  most  of  his  collections  in  small  bodies  of  water 
where  the  females  could  not  seclude  themselves  and  he  obtained  no  real 
difference  in  numbers.  My  own  collections  of  Gordius  robustus  were  made 
chiefly  at  the  egg-laying  habitats  of  the  females  and  consequently  there 
was  a  slight  predominance  of  females.  Since  in  this  species  the  males  have 
a  habit  of  remaining  for  the  greater  part  with  the  females  the  predominance 
was  not  very  large.  This  also  explains  why  very  few  specimens  of  Gordius 
robustus  are  obtained  in  general  collections.  The  males  of  Paragordius 
varius  are  more  active  in  nature  and  consequently  very  few  of  them  were 
taken  at  Urbana,  but  they  are  more  frequently  obtained  in  general  collec- 
tions. At  Douglas  Lake  I  did  not  succeed  in  finding  the  habitats  of  the 
egg-laying  females  and  as  a  result  the  females  obtained  were  chiefly  those 
that  had  just  escaped  from  their  hosts.  A  few  were  obtained  that  had 
settled  down  on  grass  near  the  shore  to  lay  eggs. 

Nothing  very  definite  can  be  said  about  the  seasonal  variations  of  the 
Gordiacea  as  reported  by  previous  workers.  The  present  investigations 
indicate  that  the  seasonal  distribution  depends  more  on  the  life  cycle  of  the 
host  than  on  the  habits  of  the  Gordiacea  themselves.  ♦ 

The  egg-laying  habits  of  the  females  and  the  possible  protection  of  the 
eggs  by  the  adults  require  some  further  explanation.    Villot  (1874)  des- 


58  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [178 

cribes  to  some  extent  the  egg-laying  habits  of  several  species.  Other  work- 
ers have  made  smaller  contributions  to  the  knowledge  of  that  subject,  but 
have  usually  assumed  that  the  observations  obtained  on  the  particular 
species  at  hand  must  hold  true  for  all  members  of  the  group.  Since  in  most 
cases  also  the  identifications  of  the  material  at  hand  were  obviously 
erroneous,  such  reports  have  done  little  more  than  add  to  the  confusion 
that  exists.  One  of  the  most  recent  of  such  reports  is  that  of  Wesenberg- 
Lund  (1910).  Some  of  its  errors  have  already  been  pointed  out  by  Miihl- 
dorf.  This  writer,  however,  does  not  himself  distinguish  clearly  between 
the  habits  of  the  different  species  under  his  observation.  From  my  own 
observations  it  is  clear  that  Wesenberg-Lund  observed  two  different 
species,  that  he  described  the  egg  strings  of  one  species,  which  he  did  not 
identify,  and  based  his  conclusions  in  regard  to  the  protection  of  the  eggs 
on  what  he  observed  in  another  species,  which  he  identified  as  Gordtus 
aquaticus. 

Of  the  first  species  he  obtained  a  single  specimen  with  a  long  string  of 
eggs  wound  around  the  stem  of  a  plant.  The  male  is  absent  and  from  the 
illustration  given  it  is  evident  that  the  female  has  no  protective  instinct, 
as  the  eggs  are  uncovered  and  partly  deserted  by  the  female.  From  the 
character  of  the  egg  string  and  the  habits  of  the  specimen  it  is  evident  that 
the  latter  belonged  to  Chordodes,  Parachordodes,  or  Paragordius. 

In  the  case  of  the  second  species  several  masses  were  observed,  but  the 
egg  strings  were  not  described.  Both  males  and  females  were  present  in  the 
mass  that  was  examined  and  pieces  of  egg  strings  were  found  when  the 
mass  was  separated  later  in  the  season.  Had  Wesenberg-Lund  separated  a 
mass  earlier  in  the  season  he  would  also  have  found  nothing  but  pieces  of 
egg  strings.  These  specimens  belonged  to  Gordius  aquaticus  or  a  closely 
related  species  which  never  lay  long  strings  of  eggs. 

In  regard  to  the  supposed  protective  instinct  of  the  parent  Gordiacea 
my  observations  confirm  those  of  Villot  and  Miihldorf,  who  were  unable 
to  find  any  evident  attempt  on  the  part  of  the  parents  to  protect  their  eggs. 
In  nature  the  specimens  of  Gordius  robustus  usually  remain  with  their  eggs 
as  in  the  case  of  the  specimens  observed  by  Wesenberg-Lund.  In  captivity 
this  species  seldom  lays  eggs  and  if  it  does  it  pays  no  attention  to  them,  but 
allows  them  to  drop  to  the  bottom  of  the  aquarium  in  small  fragments. 
JVhen  disturbed  in  nature  it  does  not  hesitate  to  abandon  the  eggs.  It 
remains  with  the  eggs  not  because  it  tries  to  protect  them,  but  merely 
because  there  is  no  stimulus  to  cause  it  to  move  on.  In  case  of  Paragordius 
varius  the  male  does  not  remain  with  the  female  even  when  undisturbed 
in  nature.  The  female  usually  remains  with  the  eggs,  but  I  have  also  found 
cases  in  which  the  eggs  were  deserted.  Even  when  the  female  remains 
with  the  eggs  it  usually  does  not  surround  them,  but  merely  remains  in  the 
same  vicinity  because  it  has  become  sluggish.    This  type  of  behavior  is 


179]  LIFE  HISTORY  OP  GORDIUS  AND  PARAGORDIUS—MA  Y  59 

indicated  by  the  figure  of  the  first  specimen  described  by  Wesenberg-Lund. 
In  neither  case  can  one  speak  of  a  true  protection  of  eggs  or  young  by  the 
parents.  Indeed,  in  case  of  the  specimens  observed  by  Wesenberg-Lund  in 
the  close  masses  it  is  very  likely  that  most  of  the  eggs  had  dropped  to  the 
bottom  of  the  pond  long  before  the  larvae  were  ready  to  hatch. 

Behavior  of  larvae 
Little  is  known  to  the  present  time  in  regard  to  the  habits  of  the  larvae, 
except  that  they  penetrate  the  tissues  of  a  great  many  animals  and  in  most 
of  them  become  encysted  and  perish  later.  Cort  (1915)  even  found  such 
encysted  larvae  in  trematodes.  Villot  (1891)  and  Camerano  (1897)  con- 
clude from  their  own  observations  that  such  encysted  forms  are  invar- 
iably lost  and  can  not  undergo  further  development.  My  observations  on 
Gordius  rohustus  show  that  an  encysted  stage  in  that  species  is  not  necessary 
and  also  that  larvae  that  have  lived  free  in  the  water  for  some  time  are 
usually  incapable  of  development. 

Infection  and  intermediate  host 
It  is  possible  in  the  light  of  the  present  evidence  to  show  that  some  of  the 
former  theories  of  infection  are  not  tenable.  The  most  commonly  accepted 
theory  in  Europe  has  been  that  which  assumes  an  active  migration  of  the 
Gordius  larvae  into  the  larvae  of  aquatic  insects  or  into  other  soft  bodied 
aquatic  animals  and  a  consequent  passive  migration  into  a  second  host, 
usually  an  aquatic  insect,  which  devours  the  first  host.  This  theory  finds 
its  support  again  in  the  recent  preliminary  account  of  the  life  history  of 
Gordius  tolosanus  published  by  Hans  Blunck.  He  differs  from  the  older 
views  in  that  they  assume  that  the  adult  Dytiscus,  to  mention  a  specific 
case,  devoured  the  infected  first  host  while  he  claims  that  the  larval  Dytis- 
cus ingests  the  first  host  and  becomes  infected.  The  older  theories  seemed 
very  logical  in  cases  where  the  final  host  was  an  aquatic  carnivore,  but 
were  difficult  to  apply  where  it  was  a  supposed  herbivore  like  a  grasshopper 
or  a  cricket.  Montgomery  supposed  in  such  cases  that  the  first  hosts  were 
perhaps  Mayfly  larvae,  that  the  encysted  parasites  were  carried  out  of  the 
water  by  the  emergence  of  the  Mayflies,  and  that  they  were  liberated  at 
the  death  of  the  insect,  remained  for  a  time  on  grass  or  leaves,  and  were 
taken  into  the  final  host  with  the  vegetable  food.  Even  as  late  as  1904  he 
had  not  discovered  that  Gryllus  abreviatus  (assimilis),  which  he  knew  to 
be  the  host  of  Paragordius  varius  is  not  only  an  omnivore  but  a  cannibal 
and  that  it  is  fond  of  its  nightly  bath.  Assuming  that  the  host  is  truly 
terrestrial,  he  went  so  far  as  to  undertake  experiments  on  desiccation  of 
worms  that  had  just  emerged  and  to  formulate  theories  in  regard  to  the 
chances  a  worm  deposited  on  dry  land  had  for  getting  back  to  the  water. 
Observations  made  during  the  present  investigations  show  that  all  hosts 
of  both  species  of  Gordiacea  here  considered  are  neither  truly  terrestrial 


00  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [180 

nor  truly  herbivorous.  There  is  then,  so  far  as  the  habits  of  the  hosts  are 
concerned,  no  reason  why  the  infection  should  not  take  place  as  indicated 
in  the  earlier  papers  of  Villot  and  Camerano  and  in  the  reports  of  most  other 
•writers.  But  the  later  conclusions  of  Villot  and  Camerano  did  not  agree 
with  the  older  views,  neither  do  the  results  of  the  present  investigation  bear 
them  out.  Those  views  have  obtained  their  greatest  support  in  the  report 
of  Blunck.  But  since  he  does  not  submit  the  facts  upon  which  his  conclu- 
sions are  based  it  is  impossible  to  know  at  present  whether  the  larvae  that 
developed  in  the  young  stages  of  Dytiscus  were  encysted  forms  that  the 
insect  had  devoured  with  prey  or  whether  they  were  larvae  that  had 
merely  adhered  to  the  food  or  had  even  bored  thru  the  external  covering 
of  the  insects  and  thus  actively  migrated  into  them.  The  mere  fact  that 
he  observed  encysted  larvae  in  the  prey  of  the  larval  beetles  would  in  no 
way  constitute  a  proof  of  the  fact  that  these  encysted  forms  were  identical 
with  the  parasitic  stages  found  later  in  the  beetles.  The  actual  evidence 
presented  up  to  the  present  time  indicates  that  there  is  in  the  life  history 
of  the  Gordiacea  no  encysted  stage  and  no  change  of  hosts.  However, 
different  species  of  the  group  may  differ  in  this  respect. 

Developmental  period 

The  conclusion  of  Svdbenik,  that  the  young  forms  must  live  several  years 
in  the  bodies  of  the  insects,  is  not  confirmed  by  the  present  report.  Blunck 
also  does  not  indicate  that  the  developmental  period  is  very  long,  as  he 
states  that  the  parasites  usually  emerge  soon  after  the  beetle  has  attained 
its  adult  form. 

The  theory  of  Villot,  Camerano  and  others  that  the  Gordiacea  fre- 
quently leave  their  hosts  before  the  cuticula  is  completely  formed  has  in 
no  way  been  confirmed  in  the  present  work.  On  the  contrary,  the  obser- 
vations show  that  in  the  species  investigated  no  essential  change  takes  place 
in  the  cuticula  after  the  specimens  have  emerged.  The  theory  was  not 
based  upon  observations  made  on  the  same  specimens  but  merely  upon  the 
fact  that  certain  specimens  presented  slightly  different  cuticular  structures 
than  did  others.  These  differences  may  have  been  due  to  the  fact  that  the 
specimens  developed  in  different  host  species  or  in  the  same  host  species 
under  different  conditions.  The  placing  of  small  or  light  colored  specimens 
in  the  category  of  young  individuals  is  based  upon  no  scientifically 
established  facts.  The  present  observations  show  that  the  statement  of 
Villot  that  young  specimens  of  Gordius  villoti  have  a  smooth  cuticula  and 
that  the  bristles  develop  later  is  founded  upon  error.  Either  the  smooth 
individuals  belong  to  a  different  species  from  the  ones  with  bristles  or  the 
European  species  is  variable  in  regard  to  that  character. 

ORGANOGENY 

In  regard  to  the  organogeny  the  work  of  Vejdovsky  (1894)  stands 
almost  alone.     The  contributions  of  Villot  on  that  subject  are  of  little 


181]  LIFE  HISTORY  OP  GORDIUS  AND  PARAGORDIUS—MA  Y  61 

scientific  value.  His  specimens  were  rendered  unfit  for  histological  inves- 
tigation by  the  methods  he  employed  in  removing  and  killing  the  parasites. 
As  proof  it  is  merely  necessary  to  consider  his  figures  and  interpretations 
of  the  hypoderm.  I  have  obtained  essentially  the  same  results  in  specimens 
that  were  removed  in  water  and  were  not  properly  killed.  In  that  case 
the  cells  shrink  and  appear  as  small,  deeply  staining  bodies  with  the  inter- 
cellular bridges  forming  radiations  from  these  centres.  The  whole  mass 
appears  as  a  network  such  as  Villot  (1874)  has  figured. 

Even  Vejdovsky's  work  is  not  free  from  similar  defects.  The  figures 
of  the  degenerating  nuclei  are  certainly  nothing  more  than  those  of  poorly 
preserved  nuclei  in  which  parts  of  the  nuclear  structures  had  been  macer- 
ated out.  Naturally  different  stages  of  such  a  process  would  be  found.  He 
supplies  part  of  the  evidence  for  that  himself  in  stating  that  the  specimens 
obtained  from  Camerano,  which  were  preserved  in  alcohol  and  were  other- 
wise in  very  poor  condition,  gave  him  the  best  results  in  the  study  of  these 
stages  in  the  nuclear  changes.  Vejdovsky  was  handicapped  in  many  ways. 
He  was  unable  to  cut  sections  less  than  20  n  thick  and  had  at  his  disposal 
no  better  stains  than  the  carmins. 

In  regard  to  the  morphology  of  the  adults  all  the  papers  except  those 
of  Montgomery,  Vejdovsky,  Rauther  and  ^vabenik  are  of  little  scientific 
value  because  the  investigations  were  either  too  fragmentary  or  they  were 
carried  out  under  conditions  that  could  produce  no  accurate  results.  The 
present  investigations  show  that  all  conclusions  based  purely  upon  adult 
structures  are  subject  to  verification.  It  is  impossible  to  interpret  properly 
the  adult  structures  of  the  Gordiacea  without  knowing  something  about 
their  development. 

Metamorphosis 

Altho  the  present  work  gives  some  information  in  regard  to  the  meta- 
morphosis of  the  two  species  studied,  there  are  many  questions  that  still 
remain  unanswered.  There  exists  no  previous  literature  on  this  subject. 
Montgomery  (1904)  and  after  him  Miihldorf  assumed  that  the  proboscis 
of  the  larva  is  a  precephalon  and  does  not  take  part  in  the  development. 
The  present  investigations  show  that  this  is  not  the  case,  but  that  the  brain 
of  the  adult  in  both  of  the  species  examined  develops  from  the  posterior 
part  of  the  proboscis,  and  that  even  the  cord  of  tissue  connecting  the  stylets 
with  the  partition  between  proboscis  and  body,  representing  possibly  the 
larval  esophagus,  develops  in  one  of  the  species. 

The  present  investigations  have  also  for  the  first  time  revealed  the  fact 
that  the  larval  cuticula  is  shed  when  the  parasite  attains  its  full  develop- 
ment and  that  the  remnants  of  the  larval  proboscis  which  do  not  take  part 
in  development  are  lost  with  the  larval  cuticula. 


O  ILUNOIS  BIOLOGICAL  MONOGRAPHS  (182 

Laier  development 

The  later  development  in  both  species  consists  of  uninterrupted  growth 
and  differentiation  from  the  time  the  first  rudiments  of  the  organs  of  the 
adult  appear  to  the  time  the  parasites  are  ready  to  leave  their  hosts. 

The  question  of  what  constitutes  a  larval  stage  in  the  Gordiacea  has 
become  even  more  complicated  thru  the  present  studies.  Villot  regarded 
the  larva  as  an  embrj^o  and  designated  the  parasitic  stage  as  larva.  Nearly 
all  other  writers  have  considered  the  stage  that  is  free  living  after  leaving 
the  egg  as  larva  and  the  later  stages  as  developmental,  young  or  juvenile. 
The  application  of  the  name  larva  to  the  parasitic  stage  was  regarded  as 
incorrect  because  it  had  no  remnant  of  the  earlier  larva  except  the  degene- 
rated proboscis  and  there  was  no  definite  change  that  marked  the  transi- 
tion between  this  stage  and  the  adult.  The  discovery  of  the  larval  cuticula 
and  the  fact  that  it  is  shed  at  the  time  the  parasite  becomes  ready  to  leave 
its  host  removes  to  a  great  extent  the  objections  to  the  application  of  the 
term  to  the  parasitic  stage,  and  the  term  larva  used  to  designate  all  the 
stages  from  the  time  the  free  living  form  emerges  from  the  egg  to  the  time 
the  parasite  is  ready  to  leave  the  host  would  certainl}^  be  justified.  But 
since  the  free  living  and  the  parasitic  stages  are  in  many  ways  completely 
different,  I  have  used  the  term  larva  in  this  paper  to  designate  only  the 
free  living  form  and  have  used  for  the  other  the  term  parasite  or  parasitic 
stage.  The  term  embryo  is  incorrectly  used  when  applied  to  the  free  living 
form.  The  other  terms  for  the  parasitic  stage  have  for  the  most  part  been 
avoided  in  this  paper  because  they  are  misleading.  The  term  juvenile  can 
be  applied  to  any  other  stage  except  the  adult.  The  term  developmental 
can  just  as  correctly  be  applied  to  the  embryological  stage  as  to  the  para- 
sitic. 

Cuticula.  During  the  entire  developmental  period  the  larval  cuticula 
expands  and  also  increases  in  thickness.  In  that  respect  it  differs  from  the 
cuticula  of  arthropods. 

The  fibrous  cuticula  of  the  adult  is  in  neither  of  the  species  a  secretion 
of  the  hypoderm,  but  a  differentiation  of  the  upper  parts  of  the  cells,  as 
was  already  pointed  out  by  Rauther.  In  other  respects  the  cuticula  in  the 
two  species  is  formed  very  differently.  In  Gordius  robustus  there  is  an 
intermediate  layer  formed  between  larval  and  the  adult  cuticula,  the  non- 
fibrous  cuticula  is  laid  down  before  the  fibrous  cuticula  begins  to  be  formed, 
the  bristles  are  projections  of  the  fibrous  cuticula,  and  there  are  no  evident 
protoplasmic  connections  between  the  non-fibrous  cuticTola  and  the  hypo- 
derm.  In  Paragordius  varius  the  larval  cuticula  remains  in  contact  with 
the  non-fibrous  cuticula,  the  structures  of  the  non-fibrous  cuticula  are 
laid  down  by  protoplasmic  strands  that  extend  up  to  it  from  the  hj^joderm 
and  are  present  even  in  the  adult,  and  the  bristles  or  tubercles  are  struc- 
tures of  the  non-fibrous  cuticula.    The  larger  radiating  fibers  that  form  the 


1831  UPE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  63 

bristles  in  Gordius  robustus  may  be  homologous  with  the  protoplasmic 
strands  in  Paragordius  varius,  but  they  do  not  appear  to  retain  living  sub- 
stance in  the  adult  condition. 

Montgomery  states  that  he  failed  to  find  any  strands  of  protoplasm 
passing  thru  the  fibrous  cuticula  of  Paragordius  varius  but  found  granules 
in  the  fibrous  cuticula  of  the  male  in  the  region  where  the  tubercles  are 
present.  He  also  figures  branching  roots  for  the  tubercles.  His  method  of 
staining  for  a  long  time  with  iron  hematoxylin  would  not  readily  bring  out 
continuous  fibers.  What  he  figures  as  granules  in  the  fibrous  cuticula  are 
undoubtedly  nothing  more  than  the  ends  of  some  of  the  protoplasmic 
strands  which  in  that  locality  are  very  large.  The  roots  of  the  tubercles 
can  be  nothing  else  than  several  pieces  of  strands  which  he  could  not  trace 
accurately  and  consequently  regarded  as  passing  to  the  same  tubercle. 
The  protoplasmic  strands  in  the  cuticula  have  been  figured  for  other  species 
of  Gordiacea,  and  Vejdovsky  (1894)  shows  them  in  definite  relation  to  the 
areolae. 

Hypoderm  and  nervous  system.  It  is  impossible  within  the  space  of  this 
paper  to  discuss  the  minor  differences  that  exist  in  the  descriptions  of  the 
h)rpoderm.  Some  of  the  artifacts  in  the  figures  of  Vejdovsky  have  already 
been  pointed  out. 

The  development  of  the  nervous  system  requires  no  further  discussion. 
In  the  structure  of  the  nerve  cord  a  minor  difference  appears  in  the  two 
species  studied,  in  Gordius  robustus  the  neural  lamella  consists  of  a  series 
of  cells  while  in  Paragordius  varius  all  the  cells  are  located  in  the  cord  it- 
self and  only  fibers  connect  the  cord  with  the  hypoderm.  The  subneural 
canal  of  Vejdovsky  was  probably  an  artifact  due  to  the  separation  of  the 
hypoderm  cells  at  the  point  where  the  fibers  from  the  cord  enter.  Rauther 
regarded  most  of  the  large  cells  of  the  nervous  system  as  belonging  to  the 
supporting  tissue.    That  is  certainly  an  error. 

The  mass  of  cells  in  Paragordius  varius  designated  by  Montgomery  as 
retina  must  be  regarded  as  the  major  part  of  the  cephalic  gangHon. 

Alimentary  canal.  The  favorite  textbook  doctrine  that  the  alimen- 
tary canal  of  the  Gordiacea  is  well  developed  and  functional  in  the  parasitic 
stages  must  be  regarded  as  disproved.  Vejdovsky  has  already  pointed  out 
that  there  is  no  difference  in  the  essential  structure  of  the  alimentary  canal 
in  the  young  forms  and  in  the  adults.  He,  however,  was  unable  to  trace 
the  origin  of  the  anterior  part  of  the  tract,  as  the  youngest  specimens 
examined  by  him  were  at  the  stage  where  the  adult  cuticula  begins  its 
formation  and  were  in  such  miserable  state  of  preservation  that  he  was 
unable  to  locate  the  gonads  in  them.  Evidently  the  entire  interior  had 
become  disintegrated.  He  found  the  larval  proboscis  at  the  point  where 
the  mouth  should  have  been,  but  in  spite  of  that  regarded  the  mouth  as 
open.    In  his  forms  the  larval  esophagus  underwent  even  more  development 


64  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [184 

than  in  Paragordius  varius.  The  brown  gland  which  he  found  in  the  region 
of  the  esophagus  is  either  homologous  with  the  part  of  the  larval  esophagus 
of  Paragordius  varius  that  grows  over  the  intestine  or  else  is  homologous 
with  the  anterior  glandular  part  of  the  intestine  itself.  The  latter  has  been 
the  opinion  of  Montgomery  and  others  who  have  studied  the  larva.  From 
the  present  investigations  it  is  evident  that  the  mouth  does  not  become 
open  until  the  adult  stage  is  reached.  In  Gordius  it  never  becomes  open; 
for  the  connection  between  the  larval  esophagus  and  the  intestine  is  severed 
at  the  very  beginning  of  the  parasitic  stage  and  no  opening  can  be  present 
after  that.  It  was  upon  examination  of  sections  of  Gordius  robustus  that 
Ward  (1892)  made  the  positive  assertion  that  in  the  specimen  examined 
there  was  no  trace  of  an  esophagus.  Others  have  obtained  similar  results 
in  this  and  related  species.  Thus  Rauther  in  the  form  he  designated  as 
Gordius  aquaticus  states  that  he  still  finds  the  mouth  opening  as  a  thin 
chitinous  tube,  but  fails  to  find  any  trace  of  an  esophagus.  Svabenik  states 
that  in  Gordius  montenegrinus  the  alimentary  canal  is  very  degenerate. 
Both  of  these  species  are  very  closely  related  to  Gordius  robustus. 

There  is  a  regression  in  the  cells  of  the  alimentary  canal  when  the  adult 
stage  is  reached,  but  it  is  not  much  more  pronounced  than  the  regression 
that  begins  at  the  same  time  in  the  other  tissues. 

The  cilia  mentioned  in  the  cloaca  and  genital  tubes  in  the  reports  of 
Montgomery  and  Rauther  have  been  explained  in  the  description  of  Para- 
gordius varius.  Rauther  also  figures  cilia  for  the  intestine  of  Gordius  tolo- 
sanus.  His  description,  however,  explains  his  error.  He  states:  "In  der 
kaudalen  Darmregion  von  G.  tolosanus  war  auch  deutlich  zu  beobachten, 
dass  die  freie  innere  Oberflache  des  Epithels  einen  sehr  regelmassigen 
fibrillar  struirten  Saum  tragt,  der  offenbar  aus  kurzen  Cilien  besteht." 
What  he  observed  was  nothing  more  than  the  inner  differentiated  zone 
that  was  in  some  cases  found  in  Gordius  robustus  in  the  present  investiga- 
tion. It  is  this  type  of  theoretical  interpretation  found  everywhere  in 
Rauther's  paper  that  makes  his  conclusions  almost  worthless.  Fortunately 
he  has  usually  given  his  actual  observations  before  interpreting  them. 
I  have  found  no  ciUa  in  the  intestine  of  either  of  the  species  studied  in  any 
stage  of  development. 

Another  case  of  Rauther's  interpretation  is  his  defense  of  Vejdovsky's 
statement  that  the  male  cloaca  is  evertable  and  serves  as  a  bursa  copula- 
trix.  He  defended  Vejdovsky's  statement  in  an  attempt  to  explain  the 
bristles  around  the  anus  of  the  male,  in  spite  of  the  fact  that  he  knew  that 
it  had  been  contradicted  by  Camerano,  von  Linfetow  and  Villot,  and  that 
he  had  observed  no  evidence  to  prove  its  correctness.  But,  the  figure 
given  by  Vejdovsky  (1886,  Fig.  31)  shows  conclusively  that  the  structure 
at  the  anal  opening  can  not  possibly  be  the  everted  cloaca.  He  shows  the 
cloaca  still  in  place  and  the  cellular  part  ending  at  the  anus.  The  part 
extruded  was  evidently  a  mass  of  spermatozoa. 


185]  LIFE  HISTORY  OP  GORDIUS  AND  PARAGORDIUS—MA  Y  65 

Muscles  and  parenchyma.  The  very  close  relationship  between  muscle 
and  parenchyma  cells  is  evident  from  the  descriptions  of  both  of  the  forms 
studied.  In  the  very  earliest  stages  observed  there  is  no  distinction  be- 
tween muscle  cells  and  mesenchyma  cells  that  later  make  up  the  paren- 
chyma. The  longitudinal  muscle  cells  can  of  course  from  their  position  be 
distinguished  in  a  general  way  from  mesenchyme  cells;  but  in  many  cases 
cells  appear  that  are  partly  within  and  partly  without  the  muscle  layer, 
and  on  account  of  the  existence  of  all  degrees  of  intercalation,  must  be 
interpreted  as  belonging  to  the  mesenchyma.  Furthermore,  the  cells  that 
line  the  hypoderm  which  later  forms  the  nerve  cord  are  at  the  earliest  stages 
not  distinguishable  from  the  muscle  cells  lining  the  rest  of  the  hypoderm. 
In  case  of  the  cloacal  muscles  all  gradations  can  be  found  between  unmis- 
takable muscle  cells  and  regular  parenchyma  cells.  All  of  these  muscles 
except  the  radiating  muscles  surrounding  the  posterior  part  of  the  cloaca 
of  the  male  develop  from  mesenchyme.  The  radiating  muscles  develop 
from  the  muscle  cells  lining  the  hypoderm  that  is  inturned  at  the  cloaca. 
From  these  facts  it  seems  probable  that  both  muscle  and  parenchyma  cells 
develop  from  mesenchyme  and  that  the  position  rather  than  any  inherent 
properties  of  the  cells  determines  whether  they  are  to  form  muscle  or  par- 
enchyma cells. 

The  fibrils  in  the  longitudinal  muscles  do  not  appear  until  the  adult 
stage  has  nearly  been  reached.  Normally  they  arrange  themselves  in  a 
row  completely  surrounding  the  rest  of  the  cell,  but  in  cases  of  excessive 
flattening  they  may  appear  to  be  interrupted  at  the  outer  edge.  Such  cells 
formed  the  basis  of  Vejdovsky's  contention  that  the  muscles  of  the  Gor- 
diacea  are  open  toward  the  hypoderm. 

In  the  light  of  the  present  investigations  the  descriptions  of  the  peri- 
toneal linings  of  epithelial  nature  must  be  regarded  as  resting  upon  misin- 
terpretations. Vejdovsky  was  the  most  positive  advocate  of  the  theory 
that  the  parenchyma  layers  are  to  be  interpreted  as  true  epithelium. 
Villot  (1881,  1887)  discovered  the  true  origin  of  the  parenchyma  layers, 
but  his  interpretation  was  not  universally  accepted  because  it  lacked 
conclusive  proof.  Von  Linstow  (1889)  also  believed  that  no  true  epithe- 
lium was  present.  Most  other  workers  were  not  inclined  to  give  any  posi- 
tive statements,  except  Svabenik,  who  followed  the  footsteps  of  Vejdovsky, 
and,  altho  his  figures  show  nothing  that  contributes  in  any  way  to  the 
knowledge  of  the  subject,  asserted  in  the  most  positive  terms  the  existence 
not  only  of  true  epithelium,  primary  and  secondary  body  cavities,  but 
also  a  rudimentary  segmentation  of  the  body  cavity. 

The  present  investigations  show  that  in  the  early  stages  there  are  no 
epithelial  layers  except  the  hypoderm  and  the  intestine,  that  the  muscles 
and  parenchyma  arise  as  mesenchyme,  and  that  the  mesenteries  and 
peritoneal  linings  are  nothing  more  than  layers  of   parenchyma.     The 


66  ILUNOIS  BIOLOGICAL  MONOGRAPHS  (186 

cavities  present  are  not  true  coelomic  cavities,  but  remnants  of  the  blas- 
tocoel  or  primary  body  cavity.  The  intestine  adheres  to  one  side  of  the 
cavity,  but  is  not  covered  by  the  peritoneal  lining.  In  the  early  stages 
the  gonads  also  are  not  covered  by  parenchyma. 

The  two  species  investigated  differ  widely  in  the  distribution  of  the 
mesenchyme  in  the  female.  In  Gordius  robustus  the  mesenchyme  does  not 
surround  the  ovaries  while  in  Paragordius  varius  it  completely  surrounds 
them. 

Vejdovsky  was  unfortunate  in  his  investigations  in  that  the  earliest 
stages  at  his  disposal  were  those  in  which  the  mesenchyme  had  just  com- 
pleted the  formation  of  the  lining  of  the  muscles  and  the  covering  for  the 
gonads.  At  that  stage  it  appears  more  like  true  epithelium  than  at  any 
other.  In  his  specimens  the  appearance  was  even  more  that  of  true  epithe- 
lium because  the  looser  mesenchyme  cells  were  not  preserved. 

No  true  circulatory  system  is  present,  but  the  body  cavities  may  be 
regarded  as  chambers  that  aid  in  the  distribution  of  liquids  in  the  body. 

No  trace  of  a  special  organ  for  excretion  is  present.  Montgomery 
found  in  one  female  an  elongated  organ  passing  along  the  dorsal  side  of 
the  anterior  part  of  the  intestine  and  at  intervals  giving  off  branches.  He 
regarded  this  as  the  vestige  of  an  excretory  organ  and  described  and  figured 
it  in  detail.  Indeed  he  described  it  so  well  that  his  error  in  interpretation 
is  easily  detected.  The  structure  was  nothing  more  than  the  mycelium 
of  a  fungus,  such  as  are  often  found  in  older  specimens.  Montgomery 
himself  states  that  "it  is  most  remarkable  that  this  organ  appears  to 
possess  no  nuclei  of  its  own.  Small  deep-staining  nuclei  are  found  in  it 
(about  29  in  number) ,  but  from  the  close  resemblance  of  these  to  the  nuclei 
of  the  parasitic  organisms  found  in  the  lumen  of  the  medio-ventral  canal, 
they  certainly  belong  to  such  parasites  which  have  penetrated  the  walls  of 
the  organ." 

Reproductive  organs.  The  origin  of  the  germ  cells  must  still  remain  a 
mystery.  That  the  bodies  found  by  Schepotieff  in  the  larval  stage  at  the 
sides  of  the  intestine  are  really  the  primordial  germ  cells  is  very  doubtful 
both  from  the  appearance  of  similar  bodies  in  other  species  and  from  his 
own  description.  In  the  larvae  of  Paragordius  varius  examined  by  me 
similar  bodies  were  present.  Montgomery  figures  two  bodies,  a  smaller  one 
anterior  and  a  larger  one  posterior,  but  states  that  more  may  be  present. 
In  the  specimens  examined  by  me  there  were  present  invariably  the  larger 
posterior  body,  which  undoubtedly  is  a  part  of  the  intestine  filled  with  a 
substance  of  nearly  homogeneous  nature,  and  two  smaller,  spherical  bodies 
with  deeply  staining  centers,  attached  to  the  antero-lateral  edges  of  the 
larger  body.  Montgomery  regards  the  substance  includecf  in  the  bodies  as 
excretory  in  nature.  In  Gordius  robustus,  where  two  bodies  appear  that 
answer  more  closely  to  the  descriptions  and  figures  of  Montgomery,  these 


187]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  67 

bodies  disappear  in  the  later  stages  and  the  intestinal  wall  in  that  region 
becomes  built  up  of  large  cells.  In  Paragordius  varius  I  have  found  no  trace 
of  the  disappearance  of  the  bodies  in  larvae  that  had  lived  in  the  free  con- 
dition for  a  long  time. 

Schepotieflf  in  his  description  says  that  the  bodies  are  formed  from  a 
vesicle  which  arises  from  the  dorsal  side  of  the  intestine.  He  states  that 
they  are  vesicles  composed  of  walls  filled  with  a  gelatinous,  feebly  staining, 
homogeneous  mass.  Each  wall  he  believes  to  contain  two  flattened  nuclei. 
He  thought  this  structure  was  similar  to  that  of  the  reproductive  tubes  of 
the  adults.  The  present  investigation,  however,  has  revealed  that  the 
gonads  in  the  early  stages  are  composed  of  cells  of  an  undifferentiated 
nature  and  consequently  it  is  doubtful  that  they  are  derived  from  larval 
structure  of  such  specialized  character. 

The  reproductive  organs  in  the  two  sexes  arise  in  the  same  manner  and 
are  differentiated  only  later  in  development.  The  term  germinal  epithe- 
lium is  hardly  applicable  to  the  early  rudiments  of  the  gonads.  Even  in 
later  stages,  with  the  exception  of  the  efferent  ducts,  no  part  of  the  repro- 
ductive columns  contains  a  structure  that  in  any  way  resembles  epithelium. 
The  resemblance  of  the  walls  of  the  oviducts  and  sperm  ducts  to  epithelium 
has  been  described  by  others.  Rauther  assumed  from  analogy  with  similar 
structures  in  other  animals  that  the  gonads  in  this  group  must  arise  as 
evaginations  of  some  epithelial  structure,  and  believed  that  the  epithelial 
remnants  presented  by  the  oviducts  indicated  that  the  evagination  had 
taken  place  at  the  point  where  the  oviducts  enter  the  cloaca.  The  results 
of  the  present  investigation  show  that  this  theory  does  not  hold.  The 
gonads  appear  some  time  before  there  is  any  trace  of  an  evagination  in  the 
region  that  later  forms  the  cloaca.  The  connection  between  gonads  and 
intestine  is  only  secondarily  acquired.  Moreover,  the  epithelial  structure 
of  the  oviducts  is  not  a  remnant  of  a  previous  epithelial  covering  of  the 
gonads,  but  a  secondary  structure  formed  by  the  rearrangement  of  cells 
that  in  the  early  stages  show  no  indication  of  an  epithelial  nature.  It  is 
possible,  of  course,  that  the  gonads  do  arise  from  the  posterior  end  of  the 
intestine,  but  in  that  case  they  are  at  first  completely  cut  off,  their  origin 
being  more  like  that  of  mesenchyme  than  of  mesothelium,  and  are  later 
reunited. 

In  later  stages  the  ovaries  are  still  essentially  like  the  testes,  except  that 
the  lower  walls  have  become  distended  at  intervals  to  allow  for  the  growth 
of  the  ova.  The  entire  ovarian  contents  are  transformed  into  germ  cells 
and  consequently  the  membranes  containing  them  have  usually  been 
regarded  as  egg  reservoirs  or  uteri.  Even  Montgomery,  who  was  aware  of 
the  true  nature  of  the  dorsal  tubes,  retained  the  name  uterus  for  them. 
He  believed  that  the  eggs  at  the  time  of  laying  pass  back  into  those  tubes 
and  backward  along  them  to  the  oviducts.    That,  however,  is  an  error.    In 


68  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [188 

Paragordius  varius  some  of  the  eggs  are  retained  in  these  tubes  and  later 
pass  back  along  them  to  the  oviducts,  but  the  majority  of  eggs  are  contained 
in  the  ovarian  buds  and  are  liberated  by  the  rupture  of  the  membranes, 
pass  back  along  the  tubes  formed  by  the  parenchymatous  walls  which 
form  the  mesenteries,  and  enter  the  oviducts  when  they  reach  the  posterior 
end.  In  Gordius  robustus  no  eggs  are  retained  in  the  primary  ovarian  tubes 
and  all  pass  back  along  the  body  cavity.  It  is  evident  from  the  descrip- 
tions given  in  this  report  that  the  only  name  applicable  to  either  a  primary 
ovarian  tube  or  the  ovarian  buds  or  both  together  is  ovary. 

The  budding  of  the  ovaries,  which  by  Vejdovsky  and  Svabenik  was 
regarded  as  rudimentary  body  metamerism,  was  found  in  the  species 
examined  to  be  highly  irregular  and  not  opposite  in  the  two  ovaries.  Con- 
sequently it  can  be  regarded  as  no  more  of  an  indication  of  true  metamerism 
than  the  branching  of  the  intestine  in  the  polyclads  or  of  the  uterus  in  some 
of  the  larger  cestodes. 

PHYSIOLOGY 

The  functions  of  the  organs  in  the  Gordiacea  are  practically  unknown. 
Interpretations  have  usually  been  made  from  analogy  with  similar  organs 
in  other  groups,  rather  than  from  actual  observations.  But  in  an  isolated 
group  like  that  of  the  Gordiacea  such  interpretations  are  very  unreliable. 
In  the  present  investigations  certain  observations  have  some  bearing  on 
the  possible  functions  of  some  of  the  organs  and  the  interpretations  are 
given  here  more  as  possibilities  than  as  certainties. 

Nutrition.  The  absorption  of  nutritive  substances  seems  to  be  carried  on 
by  the  entire  outer  body  surface.  In  the  younger  stages  of  Gordius  robustus 
the  hypoderm  cells  appear  also  to  secrete  a  digestive  substance  that  attacks 
the  cells  of  the  surrounding  tissues  of  the  host.  Thus  the  young  specimens 
enclosed  in  the  tissues  of  the  hosts  in  the  later  stages  are  always  found  in 
larger  pockets  formed  by  the  digestion  of  the  cells  immediately  surround- 
ing the  parasite.  The  digestion  does  not  appear  to  take  place  at  any  one 
point  of  the  body  of  the  parasite,  but  occurs  simultaneously  at  all  points. 
In  later  stages  even  in  Paragordius  varius  it  seems  impossible  that  any 
capillary  tube  that  may  form  the  anterior  opening  of  the  intestine  could 
supply  a  large  enough  quantity  of  fluid  from  the  body  cavity  of  the  host 
to  feed  the  developing  parasite.  In  Gordius  robustus  that  is  entirely  out 
of  the  question,  as  in  that  species  there  is  clearly  no  anterior  opening  to 
the  intestine. 

Excretion.  The  conclusion  that  the  hypoderm  and  not  the  intestine 
carries  out  digestive  functions  in  the  parasite  leaves  the  high  stage  of 
development  of  the  intestine  entirely  unexplained.  It  is,  however,  not 
necessary  to  look  far  for  the  probable  function  of  the  intestine.  It  fulfils 
every  requirement  of  an  excretory  tube.  The  resemblance  of  its  structure  to 
that  of  the  Malpighian  tubules  in  insects  is  very  close,  as  I  had  sufficient 


189]  LIFE  HISTORY  OF  GOKDIUS  AND  PARAGORDIUS—MA  7  69 

opportunity  to  observe  in  the  search  for  young  parasitic  forms  in  sections 
of  hosts.  The  tube  is  either  nearly  or  entirely  closed  at  the  anterior  end  and 
widely  open  at  the  posterior  end. 

Since  the  fluid  in  the  body  cavity  of  the  insect  is  itself  partly  excretory 
in  nature  it  is  difficult  to  understand  how  a  large  parasite  can  live  in  that 
fluid  and  possess  no  trace  of  an  excretory  system. 

Meissner  already  regarded  the  intestine  as  an  excretory  tube,  but  did 
not  recognize  its  true  ontogenetic  position  as  a  part  of  the  alimentary 
canal.  Montgomery  regarded  the  bodies  enclosed  in  the  intestine  of  the 
larva  as  excretory  in  nature. 

Functions  of  the  nervous  system.  All  reactions  in  the  two  species  observed 
are  of  a  very  low  nature.  The  most  definite  response  observed  is  the  grasping 
reaction  of  the  male  when  in  contact  with  the  body  of  the  female.  All 
other  responses  consist  merely  of  motion,  the  degree  of  motion  depending 
both  upon  the  magnitude  of  the  stimulus  and  the  state  of  activity  of  the 
specimen.  In  case  of  specimens  at  rest  it  usually  requires  several  successive 
stimuli  to  produce  any  great  irritation.  There  is  no  direct  response  to 
light  in  case  of  free  specimens,  but  the  difference  in  the  activity  of  the 
specimens  at  different  times  of  the  day  may  be  partly  due  to  the  difference 
in  the  light  intensity.  The  most  definite  case  of  orientation  to  light  is  the 
orientation  of  the  developed  specimens  in  the  abdomen  of  the  host  so  that 
the  anterior  end  is  always  at  the  point  of  exit.  This  orientation  may,  how- 
ever, be  in  part  due  to  some  other  agent.  The  emerging  reaction  on  contact 
with  water  is  next  to  the  grasping  reaction  of  the  male  the  most  definite 
response  to  stimuli,  but  the  reaction  here  is  also  nothing  more  than  motion. 


70  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [190 


RELATIONSHIPS 

The  results  obtained  in  the  present  investigations  afford  new  evidence 
both  in  regard  to  the  interrelationships  of  the  group  and  their  relations 
to  other  groups. 

From  the  descriptions  given  in  this  rep>ort  it  is  evident  that  the  two 
si>ecies  studied  differ  widely  in  regard  to  the  form  and  structure  of  the 
larva,  the  participation  of  the  proboscis  in  later  development,  the  arrange- 
ment of  the  parenchyma  in  the  female,  and  the  development  of  the  adult 
cuticula.  An  examination  of  the  literature  shows  that  these  differences  are 
not  confined  to  the  species  studied,  but  appear  in  the  same  grouping  in  aU 
cases  where  suf&cient  information  is  at  hand  to  permit  comparison.  I  have 
myself  examined  larvae  and  also  sections  of  adults  of  Chordodes  sp.  and 
find  an  essential  agreement  in  structure  with  Paragordius  varius.  The 
larva  of  Chordodes  is  even  more  abbreviated  than  that  of  Paragordius,  the 
cuticular  structures  and  the  mesenteries  are  more  pronounced,  and  the 
esophagus  is  present  in  the  adult. 

In  view  of  these  differences  I  believe  that  there  exist  in  the  present 
family  of  Gordiidae  two  well  defined,  natural  groups,  one  of  which  is 
represented  by  the  genus  Gordius  and  the  other  by  the  three  genera  Chor- 
dodes, Paragordius  and  Parachordodes.  For  that  reason  I  propose  to 
retain  the  family  Gordiidae  for  the  genus  Gordius  and  to  establish  a  new 
family,  Chordodidae,  for  the  other  three  genera. 

Since  the  p>osition  of  the  present  family  of  Nectonemidae  is  not  definite- 
ly established,  and  since  from  the  descriptions  given  Nectonema  resembles 
the  nematodes  and  especially  the  Mermithidae  in  the  structure  of  the 
muscle  cells,  the  alimentary  canal,  the  hypoderm  with  its  longitudinal 
thickenings  and  lack  of  ceU  boundaries,  the  structure  of  the  cephalic 
ganglion,  and  in  the  location  of  the  nerve  cords  within  the  thickening  of 
the  hypoderm,  it  is  not  p>ossible  to  retain  the  Nectonemidae  in  the  order 
Gordiacea.  The  family  may  for  the  present  be  assigned  to  an  independent 
position  in  the  vicinity  of  the  Nematoda. 

The  limits  of  the  old  family  Gordiidae  then  become  the  limits  of  the 
order  Gordiacea. 

The  description  of  the  proposed  family  Gordiidae  may  be  given  as 
follows:  Gordiacea  with  a  smooth  cuticula,  presenting  no  true  areoles. 
Bristles  on  the  body  arising  from  the  fibrous  cuticula.  Mouth,  when  cavity 
is  present,  not  connected  with  the  intestine.  Ovaries  not  enclosed  by 
mesenchyme  and  consequently  no  double  mesenteries  in  the  female. 


192]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  71 

Posterior  end  of  male  provided  with  two  projecting  lobes  or  prongs  arising 
a  short  distance  behind  the  anus.  A  post-anal  crescent  is  present  and  has 
its  tips  directed  toward  the  prongs.  Posterior  end  of  female  entire.  Larva 
with  elongated  body  and  pointed  posterior  end.  Only  genus  in  family: 
Gordius. 

The  limits  of  the  new  family  Chordodidae  are  the  following:  Gordiacea 
with  rough  cuticula,  presenting  true  areoles.  Tubercles  and  bristles  arising 
from  the  non-fibrous  cuticula.  Ovaries  enclosed  by  mesenchyme,  conse- 
quently double  mesenteries  present  in  the  female.  Posterior  end  of  male 
forked  or  provided  with  a  dorso-ventral  groove.  Post-anal  crescent  absent. 
Posterior  end  of  female  entire  or  provided  with  three  lobes.  Larva  with 
short  body,  rounded  at  posterior  end  and  provided  with  postero-lateral 
spines.  Genera  included  in  family:  Chordodes,  Paragordius,  Parachordodes. 

The  evidence  presented  in  this  paper  shows  clearly  that  the  supposed 
relationship  to  the  Annelida  does  not  exist.  True  coelom  and  segmentation 
are  absent.  Other  workers  have  already  shown  that  there  is  in  the  develop- 
ment of  the  Gordiacea  no  trace  of  the  trochophore  larva  of  the  Annelida. 
Almost  the  only  thing  in  common  for  the  two  is  the  ventral  position  of  the 
nerve  cord  and  its  passage  around  the  esophagus. 

The  evidence  for  a  possible  relationship  to  the  Nematoda  is  strength- 
ened by  the  discovery  of  a  moult  in  the  development  of  the  Gordiacea  and 
by  the  establishment  of  the  absence  of  cilia  or  a  true  coelom  in  that  group. 
The  absence  of  a  complicated  metamorphosis  and  the  fact  that  the  pro- 
boscis is  not  exclusively  a  larval  organ  remove  some  of  the  objections  to 
such  a  relationship. 


n  ILUNOIS  BIOLOGICAL  MONOGRAPHS  (192 


BIBLIOGRAPHY 

Baird,  W. 

1853.    Descriptions  of  some  New  Species  of  Entozoa  from  the  Collection  of  the  British 
Museum.    Proc  ZooL  Soc  London,  part  21,  pp.  18-25. 
Blunck,  Hans. 

1915.    Ein  kurzes  Wort  zur  Kenntniss  der  Gordiiden-biologie.    Zool.  Anz.,  45:289-290. 
Bock,  S. 

1913.    Zur  Kenntniss  von  Nectonema  und  dessen  systematischer  Stellimg.  Zool.  Bidrag, 
Upsala,  2:1-28;  2  fd. 
BteGER,  0. 

1891.  Zur  Kenntniss  von  Nectonema  agile  Verr.    ZooL  Jahrb.,  Anat.,  4:631-652;  1  pL 
Camerano,  L. 

1886.  Ricerche  intomo  alle  specie  Italiene  del  genere  Gordius.    Atti  R.  Accad.  Sd. 
Torino,  22:145-175;  1  pi. 

1887.  Osservazioni  sui  caratteri  diagnostici  dei  Gordius  e  sopra  alcune  specie  de  Gordius 
d'Europa.    Boll.  Mus.  Zool.  Torino,  2,  no.  24,  10  pp. 

1887a.  Nota  intomo  alia  struttura  della  cuticola  del  Gordius  tricuspidatus  (L.  DuL). 
Boll.  Mus.  Zool.  Torino,  2,  no.  25. 

1888.  Ricerche  intomo  alia  anatomia  ed  istologia  dei  GordiL    Boll.  Mus.  Zool.  Torino, 
3;  63  pp.,  9  pi. 

1888a.  Recherches  sur  I'anatomie  et  I'histologie  des  Gordiens.    Arch.  Ital.  Biol.,  9:243- 

248. 
1888b.  Ricerche  intomo  al  parassitismo  ed  al  polimorfismo  dei  Gordii.    Mem.  R.  Accad. 

Sd.  Torino,  (2)  38:395-413. 
1890.    I  primi  momenti  della  evoluzione  dei  Gordii.  Mem.  R.  Accad.  Sd.  Torino,  (2) 

40:1-19;  2  pi. 

1892.  Ricerche  intomo  al  parassitismo  ed  alio  sviluppo  dd  Gordius  pustulosus  Baird. 
Atti  R.  Accad.  Sci.  Torino,  27:598-607;  1  pi. 

1897.  Nuova  dassificadone  dei  Gordii.    Zool.  Anz.,  20:225-229. 

1897a.  Monografia  dei  Gordii.    Mem.  R.  Accad.  Sd.  Torino,  (2)  47:339-419;  3  pi. 

1898.  Gordiens  du  Mexique.    Bull.  soc.  zool.  France,  23:73-76. 
CORT,  W.  W. 

1915.    Gordius  Larvae  Parasitic  in  a  Trematode.    Jour.  ParasiL,  1:198-199. 
Creplin,  F.  C. 

1847.    Chordodes  parasitus,  ein  Schmarotzerwurm  aus  einer  Heuschrecke.    (Frorieb's 
Notiz.)    N.  Notiz.  Geb.  Nat.  Heilk.,  Weimar,  3R  (55),  3:161. 
DujARDm,  F. 

1842.    M6moir  sur  la  structure  anatomique  des  Gordius  et  d'un  autre  helminthe,  le 
Mermis,  qu'on  a  confondu  avec  eux.    Ann.  sci.  nat.,  zool.,  (2)  18:129-151,  1  pL 
Grenacker,  H. 

1868.  Zur  Anatomie  der  Gattung  Gordius  L.    Zeit.  wiss.  Zool.,  18:322-344;  2  pL 

1869.  Ueber  die  Muskelelemente  von  Gordius.    Zeit  wiss.  Zool.,  19:287-288. 
Grube,  E. 

1849.    Ueber  einige  Anguillulen  und  die  Entwicklung  von  Gordius  aquaticus.    Aich. 
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HoniANNER,  B. 

1913.    Gordiiden  imd  Mennithiden  aus  dem  thurgauischen  naturhistorischen  Museimi 
zu  Frauenfdd.    Mitt.  Thurgau.  Nat.  Ges.,  20:282-286. 


193]  LIFE  HISTOR Y  OG  GORDIUS  AND  PARAGORDIUS—MA  Y  73 

Janda,  J. 

1894.    Beitrage  zur  Systematik  der  Gordiiden.    Zool.  Jahrb.,  Syst.,  7:595-612;  2  pi. 
Leidy,  J. 

1851.    Gordiaceae.    Proc.  Acad.  Nat.  Sci,  Phila,,  5:262-263,  275. 

1879.    On  Gordius,  and  on  some  Parasites  of  the  Rat.    Proc.  Acad.  Nat.  Sci.  Phila., 
pp.  10-11. 
Linnaeus,  C. 

1758.    Systema  Naturae.    10th  ed. 

LiNSTOW,  O.  VON. 

1889.     Ueber  die  Entwicklungsgeschichte  und  die  Anatomie  von  Gordius  tolosanus 

Duj.  =G.  subbifurcus  v.  Siebold.     Arch.  mikr.  Anat.,  34:248-268;  3  pi. 
1891.    Weitere  Beobachtungen  an  Gordius  tolosanus  nnd  Mermis.    Arch.  mikr.  Anat., 

37:239-249;  1  pi. 
1891a.  Ueber  die  Entwickelungsgeschichte  von  Gordius  tolosanus  Duj,    Cent.  Bact. 
Parasit.,  9:760-762. 
Magath,  T.  B. 

1916.    Nematode  Technique.    Trans.  Amer,  Micr.  Soc.,  35:245-256. 
Meissner,  Geo. 

1855.    Beitrage  zur  Anatomie  und  Physiologic  der  Gordiaceen.    Zeit.  wiss.  Zool.,  7: 
1-144;  7  pi. 
Meyer,  N.  Th. 

1913.    Zur  Entwicklung  von  Gordius  aquaticus  Villot.     Zeit.  wiss.  Zool.,  105:125-135; 
2  pi. 
Michel,  A. 

1888.    De  I'existence  d'un  v6ritable  dpiderme  cellulaire  chez  les  Nematodes,  et  special- 
ment  les  Gordiens.  C.  R.  acad.  sci.  Paris,  107:1175-1177. 
MoBius,  K. 

1855.    Chordodes  pilosus,  ein  Wurm  aus  der  Familie  der  Gordiaceen.    Zeit.  wiss.  Zool., 
6:428-431;  1  pi. 
Montgomery,  T.  H.  Jr. 

1898.  The  Gordiacea  of  Certain  American  Collections  with  Particular  Reference  to  the 
North  American  Fauna.    Bull.  Mus.  Comp.  Zool.  Harvard,   32:23-59;  15  pi. 

1898a.  The  Gordiacea  of  Certain  American  Collections,  with  Particular  Reference  to  the 
North  American  Fauna,  11.    Proc.  Cal.  Acad.  Sci.,  Zool.,  (3)  1:333-344;  2  pi. 

1899.  Synopses    of    North- American   Invertebrates.    II.  Gordiacea    (Hair   Worms). 
Amer.  Nat.,  33:647-652. 

1900.  Gordiacea  from  the  Cope  Collection.    Biol.  Bull.,  1. -95-98. 

1903.  The  Adult  Organization  of  Paragordius  varius  (Leidy).     Zool.  Jahrb.,  Anat., 
18:387-^74;  7  pi. 

1904.  The  Development  and  Structure  of  the  Larva  of  Paragordius.    Proc.  Acad.  Nat. 
Sci.  PhUa.,  56:738-755;  2  pi. 

1907.    The  Distribution  of  the  North  American  Gordiacea,  with  Description  of  a  New 
Species.    Proc.  Acad.  Nat.  Sci.  Phila.,  59:270-272. 

MtJHLDORF,  A. 

1913.  Studien  fiber  die  Entwicklung  der  Nematomorphen  (Vejd.).    Zool.  Anz.,  42:31- 
36. 

1914.  Beitrage  zur  Entwicklungsgeschichte  und  zu  den  phylogenetischen  Beziehungen 
der  Gordiuslarve.    Zeit.  wiss.  Zool.,  Ill :l-75;  3  pi. 

Rauther,  Max. 

1904.    Das  Cerebralganglion  und  die  Leibeshohle  der  Gordiiden.    Zool.  Anz.,  27:606- 
614. 


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1905.     Beitrage  zur  Kenntniss  der  Morphologic  und  der  phylogenetischen  Beziehungen 
der  Gordiiden.     Jena.  Zeit.,  40:1-94;  4  pi. 
Rehn,  J.  A.  G.  and  Hebakd,  M. 

1915.    The  Genus  Gryllus  (Orthoptera)  as  found  in  America.    Proc.  Acad.  Nat.  Sci. 
Phila.,  67:293-322;  1  pi. 
Ritchie,  Jajies. 

1915.     Scottish  Hairwonns  (Nematomorpha,  Gordiidae),  their  Occurrence,  Habits,  and 
Characteristics;  with  a  Key  for  the  Discrimination  of  the  Species  Recorded  from 
Britain.    Scottish  Nat.,  pp.  111-115,  136-142,  255-262. 
RdKER,  F. 

1897.  Beitrag  zur  Systematik  der  Gordiiden.  Abh.  Senckenberg.  Naturf.  Ges.,  23:247- 
295;  1  pi. 

Rosa,  D. 

1882.  Nota  intomo  al  Gordius  villoti  n.  sp.  ed  al  G.  tolosanus  Duj.  Atti  R.  Accad.  Sci. 
Torino,  17:333-342;  1  pi. 

SCHEPOXrEFF,  A.  , 

1908.    Ueber  den  feineren  Bau  der  Gordiuslarven.    Zeit.  wiss.  Zoo!.,  89:230-241;  1  pi. 
Stiles,  C.  W. 

1907.  Three  new  American  Cases  of  Infection  of  Man  with  Horse-Hair  Worms  (Species 
Paragordius  varius),  with  Summary  of  all  Cases  Reported  to  Date.  Hyg.  Lab.* 
Bull.  34,  pp.  53-68. 

SvABENiK,  Jan. 

1908.  Studien  an  Nematomorphen.    2^1.  Anz.,  33:385-388. 

1910.    Beitrage  zur  Anatomie  imd  Histologic  der  Nematomorpha.    Sitzungsber.    K. 
Bohm.  Ges.  Wiss.,  math.-naturw.  Classe,  1909,  no.  7,  64  pp.,  1  pi. 
Ulrey,  a.  B. 

1898.  Notes  on  the  Embryology  of  Paragordius  (Gordius)  varius  (Leidy).    Proc 
Indiana  Acad.  Sci.,  1897:232-233. 

Vejdovsky,  F. 

1886.    Zur  Morphologic  der  Gordiiden.    Zeit.  wiss.  Zool.,  43:369-433;  2  pis. 

1888.  Studien  uber  Gordiiden.  (Zweite  Mittheilung.)  Zeit.  wiss.  Zool.,  46:188-216 
Ipl. 

1894.  Organogenic  der  Gordiiden.     (Zugleich  ein  Beitrag  zur  Kenntnis  der  Meta 
<  morphosc  und  Biologic  der  Zelle.)     Zeit.  wiss.  Zool.,  57:642-703;  4  pi. 

1898.    Bemerkungen  zu  den  Gordiidenarbeiten  von  Linstow's.    Zool.  Anz.,  21:382-384 

VnxoT,  A. 

1874.    Monographic    des    Dragonneaux.     (Genre    Gordius,    Dujardin.)     Arch,    zool 

exp^r.,  3:39-72,  181-238;  6  pi. 
1881.    Nouvclles  recherches  sur  I'organisation  et  le  d6veloppement  des  Gordiens.    Ann 

sci.  nat.,  zool.,  (6)  ll:l-44j  2  pi. 

1886.  Revision  des  (iordiens.    Ann.  sci.  nat.,  zool.,  (7)  1:271-318;  3  pL 

1887.  Sur  Tanatomie  des  Gordiens.    Ann.  sci.  nat.,  zool.,  (7)  2:189-212. 

1889.  Sur  rhypoderm  ct  Ic  systeme  nerveux  peripherique  des  Gordiens.  C.  R.  acad. 
sci.  Paris,  108:304-306. 

1889a.  Sur  I'ovogen^se,  la  structure  de  I'ovaire  et  la  regression  du  parenchyme  des  Gor- 
diens.    C.  R.  acad.  sci.  Paris,  109:411-412. 

1889b.  Sur  la  signification  histologique,  le  mode  de  formation  et  I'usage  de  la  cavit6 
p6ri-intcstinale  des  Gordiens.     C.  R.  acad.  sci.  Paris,  108:685-687. 

1891.    L'Evolution  des  Gordiens.    Ann.  sci.  nat.,  zool.,  (7)  11:329-401;  3  pi. 

1895.  Le  polymorphisme  des  Gordiens.     C.  R.  assoc.  franc,  avanc.  sci.,  23(2):659-664. 


195]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  75 

1896.    Le  polymorphisme  du  "Gordius  violaceus."     C.  R.  assoc.  franc,  avanc.  sci., 

24(2):650-657. 
1X96a.  Reclamation  de  priority  sur  rembryog^nie  des  Gordiens  et  des  Nematoldes. 

Zool.  Anz.,  19:123-125. 
Ward,  H.  B. 

1892.    On  Nectonema  agile,  Verrill.    Bull.  Mus.  Comp.  Zool.  Harvard,   23:135-188; 

8  pi. 
Wesenberg-Lund,  C. 

1910.    Uber  eine  eventuelle  Brutpflege  bei  Gordius  aquaticus  L.    Intern.  Rev.  Ges. 

Hydrobiol.,  3:122-127. 


76  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [196 


EXPLANATION  OF  PLATES 

Plate  I  consists  of  photomicrographs  made  from  slides.  The  other 
figures  were  drawn  either  from  slides  by  means  of  a  camera  lucida  or  from 
photographs  by  means  of  a  copying  lens.  Magnifications  were  obtained 
in  case  of  drawings  by  the  projection  of  the  stage  micrometer  scale  on 
the  paper  and  in  case  of  photographs  by  projecting  the  stage  micrometer 
scale  on  the  focussing  screen. 

The  original  thesis  deposited  in  the  library  of  the  University  of  Illinois 
contains  656  figures,  of  which  all  but  twelve  are  photomicrographs.  Those 
photographs  illustrate  many  points  in  the  description  that  could  not  be 
shown  in  the  drawings. 

The  author  is  indebted  to  the  University  of  Illinois  for  special  services 
from  an  artist  of  the  university  to  draw  a  number  of  the  figures.  He  is 
likewise  indebted  to  the  Zoological  Division  of  the  Bureau  of  Animal 
Industry  at  Washington,  D.  C.  for  permitting  the  artist  of  the  division 
to  draw  a  large  number  of  the  figures. 

The  abbreviations  I  4,  I  7,  and  I  8,  as  used  in  the  descriptions  of 
figures,  are  the  serial  numbers  of  the  infection  experiments  and  are  de- 
scribed in  the  section  on  parasitism  in  Gordius  robustus. 


197J  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  77 


PLATE  I 


78  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [198 


EXPLANATION  OF  PLATE 
Photomickogpaphs  or  Mounxs 

Fig.  1. — Paragordius  varius,  tangential  section  of  fibrous  cuticula  of  adult;  shows  fibres,  ends 

of  radiating  strands,  and  cross  formed  by  the  passage  thru  the  cuticula  of  a  large  strand 

to  a  tubercle;  X  800. 
Fig.  2. — P.  varius,  longitudinal  section  of  young  female;  shows  that  buds  of  ovaries  are  not 

opposite;  X  50. 
Fig.  3. — P.  varius,  longitudinal  section  thru  anterior  end  of  adult,  showing  large  parenchynm 

cells;  X  100. 
Fig.  4. — Gordius  robustus,  thin  layer  of  fibrous  cuticula  of  adult  after  maceration  with  nitric 

acid;  X  1240. 
Fig.  5. — Same  as  Fig.  4;  X  175. 
Fig.  6. — P.  varius,  longitudinal  section  perpendicular  to  surface  of  muscle  cells  of  adult;  shows 

elongated  condition  of  cells  and  nuclei;  X  150. 
Fig.  7. — P.  varius,  tangential  section  thru  wall  of  cloaca,  showing  pores;  X  475. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


i 


MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  I 


1991  LIP^  HISTORY  OP  GORDIUS  AND  PARAGORDIUS—MA  Y  79 


PLATE  II 


80  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [200 


EXPLANATION  OF  PLATE 
Gordius  robustus 

Fig.  8. — ^Posterior  end  of  male;  end  view,  slightly  ventral;  free  hand  sketch  from  alcoholic 

specimen;  X  20. 
Fig.  9. — Six  day  specimen  from  1 4;  posterior  end  turned  up  and  not  shown;  X  250. 
Fig.  10. — Section  thru  sperm  mass  just  posterior  to  anal  opening  of  female;  shows  free  area 

where  spermatozoa  have  migrated  into  cloaca;  X  250. 
Fig.  11. — Six  day  specimen  from  I  4;  large  nuclei  in  anterior  end  of  intestine;  X  385. 
Fig.  12. — Spermatozoa  in  anterior  end  of  male  in  which  the  adult  cuticula  is  not  fully  develop- 
ed; X  800. 
Fig.  13. — Spermatozoa  from  posterior  end  of  same  specimen  as  in  Fig.  12;  X  800. 
Fig.  14. — Larva  after  prolonged  free  existence;  side  view;  drawn  in  optical  section  from  stained 

specimen  cleared  in  oil  of  wintergreen;  X  1200. 
Fig.  15. — Eight  day  specimen  from  I  8;  intestine  with  large  nuclei  at  anterior  end;  cells  in 

cephalic  ganglion  somewhat  enlarged;  X  190. 
Fig.  16. — Adult  cuticula;  surface  view,  showing  intersecting  lines  and  light  spots;  drawn  to 

scale  from  living  specimen  obtained  from  Mt.  Vernon,  Illinois;  X  30. 
Fig.  17. — Spermatozoa  from  seminal  receptacle  of  female;  X  800. 
Fig.  18. — Mature  spermatozoa  from  male;  X  800. 
Fig.  19. — Spermatozoa  in  section  of  adult  male;  X  800. 
Fig.  20. — ^Larva  just  hatched;  side  view;  drawn  in  optical  section  from  stained  specimen 

cleared  in  oil  of  wintergreen;  X  1325. 
Fig.  21. — Proboscis  of  free  living  larva;  section;  X  800. 
Fig.  22. — ^Anterior  tip  of  parasitic  form,  showing  larval  hooks;  X  240. 
Fig.  23. — Section  just  posterior  to  preceding;  X  240. 
Fig.  24. — Posterior  end  of  white  male,  nearly  adult;  side  view;  X  25. 
Fig.  25. — Posterior  end  of  white  female,  nearly  adult;  semi  transparent;  side  view;  X  25. 
Fig.  26. — ^Posterior  end  of  adult  female;  dorsal  view;  drawn  from  alcoholic  specimen;  X  25. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


23  -^^24 

GORDIUS  AND  PARAGORDIUS 


^,    '  / 


«?■: 


■jftf.; 


^V^^' 


^a 


201]  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MAY  81 


PLATE  III 


82  ILUNOJS  BIOLOGICAL  MONOGRAPHS  [202 


EXPLANATION  OF  PLATE 
Gordius  robustus 
Fig.  27. — ^Anterior  end  of  adult  male;  dorsal  view,  drawn  from  alcoholic  spcdmen;  X  25. 

Fig.  28. — Anterior  end  of  female,  Leidy  collection  of  1879;  dorsal  view;  drawn  from  alcoholic 

q>ecimen;  X  25. 
Fig.  29. — Section  thru  posterior  aid  of  young  male,  showing  jimction  of  q)erm  ducts  and 

intestine;  X  360. 
Fig.  30. — Male  and  female;  early  stage  in  process  of  mating;  sketch  from  living  specimens; 

XIO. 
Fig.  31. — ^Male  and  female;  just  before  discharge  of  sperm;  X  10. 

Fig.  32. — ^Posterior  end  of  adult  male;  ventral  view;  drawn  from  alcoholic  specimen;  X  40. 
Fig.  33. — End  view  ot  anterior  end;  drawn  from  alcoholic  specimen;  X  50. 
Iig.  34. — ^Posterior  end  of  adult  female;  end  view;  drawn  from  alcoholic  specimen;  X  50. 
Fig.  35. — Early  stage  in  the  development  of  adult  cuticula;  X  480. 
Fig.  36. — Cross  section  thru  base  of  fork  of  male;  adult  cuticula  not  completely  formed;  shows 

canal  passing  from  end  of  intestine  to  outlet  in  larval  cuticula  at  tip  of  fork;  X  120. 
Fig.  37. — Sagital  section  thru  postcloacal  ridge  of  young  male;  X  140. 
Fig.  38. — Structure  of  adult  cuticula;  X  440. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


38 

PLATE  III 


203 1  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  83 


PLATE  IV 


84  ILUNOIS  BIOLOGICAL  MONOGRAPHS  1204 


EXPLANATION  OF  PLATE 

Gordius  robustus 

Fig.  39. — Cross  section  in  front  of  cephalic  ganglion  in  specimen  shedding  the  larval  cuticula; 

X90. 
Fig.  40. — ^Longitudinal  section  of  specimen  with  adult  cuticula  nearly  completed;  shows  spine 

in  early  development  with  minute  fibre  barely  traceable  to  hypoderm;  X  870. 
Fig.  41. — Hypoderm  and  the  formation  of  granular  layer  under  larval  cuticula;  X  500. 
Fig.  42. — Cross  section  of  specimen  with  developing  cuticula;  shows  nerve  cell  and  fibre  in 

hypoderm;  X  450. 
Fig.  43. — Stage  in  the  development  of  adult  cuticula  later  than  that  shown  in  Fig.  35;  cuticula 

has  attained  about  half  its  final  diameter;  X  450. 
Fig.  44. — ^Late  stage  in  development  of  adult  cutiaila,  longitudinal  section;  shows  bristle 

passing  thru  granular  layer;  X  665. 
Fig.  45. — Section  parallel  to  neural  lamella  in  specimen  nearly  mature;  shows  bipolar  cells; 

X  320. 
Fig.  46. — Cross  section  thru  body  of  female  that  has  deposited  its  eggs;  shows  tissues  partly 

degenerated;  X  135. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


imqfmm 


45 


MAY 


GORDIUS  AND  PARAGORDIUS  PLATE  IV 


-^^■>'^■ 


■2sC-5^-" 


f?'-- 


2051  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  85 


PLATE  V 


86  ILUNOIS  BIOLOGICAL  MONOGRAPHS  (206 


EXPLANATION  OF  PLATE 

Gordius  robustus 
Fig.  47. — Three  day  spedmen  from  1 7;  cross  section  of  stylets  in  tissues  of  host;  X  640. 
Fig.  48. — ^Adjacent  section  posterior  to  Fig.  47;  cross  section  of  hooks  of  proboscis  in  tissues 

of  host;  X  640. 
Fig.  49. — ^Adjacent  section  posterior  to  Fig.  48;  muscles  in  proboscis;  X  640. 
Fig.  50. — Five  day  specimen  of  I  7;  section  thru  anterior  end  and  middle  of  body  in  tissues 

of  host;  X  480.  , 

Fig.  51.— Section  adjacent  to  Fig.  50;  X  480. 
Fig.  52.— Section  adjacent  to  Fig.  51;  X  480. 

Fig.  53. — ^Section  thru  extreme  ends  of  same  specimen;  hooks  in  proboscis;  X  480. 
Fig.  54.— -Section  of  seven  day  specimen  of  I  7  in  tissues  of  host;  X  225. 
Fig.  55. — Section  of  nine  day  specimen  of  I  7  in  tissues  of  host;  X  225. 
Fig.  56. — ^Twenty-eight  day  spedmen  of  I  8;  tangential  section  thru  hyjxxierm,  showing  the 

two  rows  of  nerve  cells;  X  220. 
Fig.  57. — ^Twelve  day  specimen  of  I  7;  cross  section  thru  anterior  end,  showing  proboscis  mus- 

des;  X  400. 
Fig.  58. — ^Twenty-dght  day  specimen  of  1 8;  cross  section  near  anterior  end;  X  220. 
Fig.  59. — Sagittal  section  thru  posterior  end  of  yoimg  male;  anus  still  opens  terminally;  X  70. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


207]  UFE  HISTORY  OF  CORDIUS  AND  PARAGORDIUS—MA  Y  87 


PLATE  VI 


ILUNOIS  BIOLOGICAL  MONOGRAPHS  [208 


EXPLANATION  OF  PLATE 
Gordius  robustus 

fig.  60. — ^Sagittal  section  thru  posterior  end  of  young  male;  slightly  older  than  that  of  Hg. 
59i  X  70. 

Fig.  6L — Similar  section  thru  still  older  specimen;  X  70. 

Iig.  62. — ^Young  female;  longitudinal  section,  showing  budding  of  ovaries;  buds  not  opposite; 
X55. 

Fig.  63. — ^Twelve  day  specimen  of  I  7;  oblique  section  of  posterior  end,  showing  early  intes- 
tinal diverticula  where  reproductive  organs  later  join;  X  400. 

Fig.  64. — Similar  section  thru  another  specimen  of  the  same  lot;  X  400. 

Kg.  65. — ^Twenty-eight  day  specimen  of  I  8;  cross  section  of  posterior  end,  showing 
intestinal  diverticula;  X  400. 

Kg.  66. — ^Twelve  day  specimen  of  I  7;  cross  section;  X  400. 

Fig.  67. — ^Twelve  day  specimen  of  I  7;  longitudinal  section  of  anterior  end;  shows  disinte- 
gration of  cells  in  anterior  p>art  of  intestine,  cephalic  ganglion  in  early  stage,  and  tissue 
growing  in  between  intestine  and  cephalic  ganglion;  X  400. 

Fig.  68. — Similar  section  of  another  specimen  of  the  same  lot;  X  400. 

Fig.  69. — Similar  section  of  specimen  from  same  lot;  X  400. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS  PLATE  Vl 


2091  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  89 


PLATE  VII 


90  ILLINOIS  BIOLOGICAL  MONOGRAPHS  (210 


EXPLANATION  OF  PLATE 

Gordius  robustus 

Fig.  70. — Young  male;  section  near  posterior  end;  junction  of  intestine  and  sperm  ducts; 
X  380. 

Fig.  71. — Cross  section  posterior  to  that  of  Fig.  70;  X  380. 

Fig.  72. — ^Young  male;  same  specimen  as  Fig.  29;  section  thru  middle  of  body;  X  380. 

Fig.  73. — ^Anterior  end  of  young  specimen;  longitudinal  section;  shows  intestine  ending  con- 
siderably posterior  to  cephalic  ganglion,  renmants  of  proboscis,  and  cord  connecting 
stylets  with  partition  between  body  and  proboscis;  X  220. 

Fig.  74. — Similar  section  of  specimen  almost  fully  developed;  X  105. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS  PLATE  VII 


i:-%,         t 


J^«^/...'7- 


-«  I    !..,:.     . 


2111  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  91 


PLATE  VIII 


92  I LUNOIS  BIOLOGICAL  MONOGRAPHS  [212 


EXPLANATION  OF  PLATE 

Gordius  robustus  "* 

Fig.  75. — Cross  section  of  male  somewhat  older  than  that  of  Fig.  72;  X  195. 
Fig.  76. — Cross  section  thru  young  female  of  about  the  same  age;  X  195. 
Fig.  77. — Cross  section  thru  female  with  adult  cuticula  nearly  complete;  X  60. 
Fig.  78. — Sagittal  section  thru  posterior  end  of  female,  nearly  adult;  X  55. 
Fig.  79. — Female  at  beginning  of  formation  of  adult  cuticula;  cross  section  near  anterior  end 

of  body;  X  130. 
Fig.  80. — Cross  section  of  male  in  same  stage  of  development  as  female  of  Fig.  77;  X  80. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


79  ^^4?   <ii|liil|iWMIPi  h^J^    80 

GORDIUS  AND  PARAGORDIUS  PLATE  VIII 


"^j^' 


2131  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—UA  Y  93 


PLATE  IX 


94  ILLINOIS  BIOLOGICAL  MONOGRAPHS 


EXPLANATION  OF  PLATE 
Gordius  robustus 

Fig.  81. — Cross  section  thru  cephalic  ganglion  just  before  formation  of  adult  cuticula;  early 

large  cells  near  middle  of  section;  X  160, 
Fig.  82. — ^Adjacent  section  just  posterior  to  that  of  Fig.  81;  X  160. 
Fig.  83. — Adjacent  section  posterior  to  that  of  Fig.  82;  X  160. 
Fig.  84. — ^Young  female;  buds  forming  on  ovarian  tubes;  X  270. 
Fig.  85. — Early  stage  in  development  of  adult  cuticula;  formation  of  hyaline  layer  outside 

of  adult  cuticula;  X  640. 
Fig.  86. — ^Young  female;  cross  section  showing  early  growth  period  in  oocytes;  X  170. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  IX 


215]  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDWS—MA  Y  95 


PLATE  X 


96  ILLINOIS  BIOLOGICAL  MONOGRAPHS  \2\6 


EXPLANATION  OF  PLATE 
Gordius  robustus 

Fig.  87. — Female  at  beginning  of  formation  of  adult  cuticula;  cross  section  near  middle  of  body ; 

X95. 
Fig.  88. — Section  near  posterior  end  of  same  female;  seminal  receptacle  and  ovaries  just 

before  they  pass  over  into  the  oviducts;  X  105. 
Fig.  89.— Section  slightly  posterior  to  that  of  Fig.  88;  X  105. 
Fig.  90.— Section  slightly  posterior  to  that  of  Fig.  89;  X  105. 
Fig.  91. — Section  thru  posterior  end  of  cloacal  gland  of  same  female;  X  105. 
Fig.  92. — Section  behind  cloacal  gland  of  same  female;  cloacal  ganglion;  X  140. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  X 


-98  ILLINOIS  BIOLOGICAL  MONOGRAPHS  1218 


EXPLANATION  OF  PLATE 
Gordius  robustus 

Fig.  93. — Section  thru  anterior  end  of  cloacal  gland  of  female  shown  in  Plate  10;  oviducts, 

intestine,  and  posterior  end  of  seminal  receptacle;  X  105. 
Fig.  94. — Section  thru  constriction  between  cloacal  gland  and  seminal  receptacle;  circular 

musculature  surrounding  constriction;  X  105. 
Fig.  95. — Section  posterior  to  that  of  Fig.  94;  entrance  of  oviducts  into  cloaca;  X  105. 
Fig.  96. — Cross  section  thru  cloacal  musculature  of  male,  nearly  adult;  just  behind  anus;  X  90. 
Fig.  97.— Section  a  short  distance  behind  that  of  Fig.  96;  X  90. 
Fig.  98. — Section  thru  crescent  of  same  male;  X  90. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


2191  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  99 


PLATE  XII 


100  I LUNOIS  BIOLOGICAL  MONOGRAPHS  1220 


EXPLANATION  OF  PLATE 

Fig.  99. — Gordius  robustus,  section  thru  cloacal  ganglion  of  same  female  as  Fig.  95;  X  105. 
Fig.  100. — G.  robustus,  section  slightly  posterior  to  that  of  Fig.  99;  intestine  enters  cloaca; 

X  105. 
Fig.  101. — G.  robustus,  sagittal  section  thru  cloacal  ganglion  of  male;  crescent  in  process  of 

formation;  X  105. 
Fig.  102. — G.  robustus,  same  section  as  Fig.  101;  X  340. 

Fig.  103. — Paragordius  varius,  cross  section  thru  female  that  has  deposited  its  eggs;  X  70. 
Fig.  104. — P.  varius,  tangential  section  thru  developing  adult  cuticula;  areolae  in  the  process 

of  formation;  X  400. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


/•'    m'^  ^'-Ji 

"*•%.•*• 

^      '» 

-*^ 

"      *  *" 

«•  r>  « 

^-V- 

•^• 

. 

--  •* 

MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  XII 


jp 


211]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  101 


PLATE  XIII 


1Q2  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [212 


EXPLANATION  OF  PLATE 
Gordius  robustus 
Fig.  105. — Cross  section  of  nerve  cord  of  adult;  X  700. 

Fig.  106. — ^Nerve  cord  in  specimen  with  adult  cuticula  nearly  complete;  X  340. 
Fig.  107. — Section  near  posterior  end  of  male  with  fibrous  cuticula  nearly  complete;  X  120. 
Fig.  108. — ^Section  thru  anterior  end  of  same  specimen  as  Fig.  107;  X  120. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS  PLATE  XIII 


223  ]  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  103 


PLATE  XIV 


104  ILUNOIS  BIOLOGICAL  MONOGRAPHS  fjjl 


EXPLANATION  OF  PLATE 

Gordius  robustus 

Fig.  109. — ^Young  female;  cross  section  near  posterior  end;  early  stages  of  oviducts,  seminal 

receptacle,  and  cloacal  gland;  X  250. 
Fig.  110.— Section  slightly  posterior  to  that  of  Fig.  109;  X  250. 
Fig.  111. — Section  thru  posterior  end  of  cloacal  gland  of  same  female;  X  250. 
Fig.  112. — Development  of  cuticula  and  muscles;  slightiy  later  stage  than  Fig.  85;  X  720. 
Fig.  113. — Cross  section  thru  posterior  region  of  female  showing  mass  of  spermatozoa  adhering 

to  outside;  X  60. 
Fig.  114. — Cross  section  of  nerve  cord  of  adult;  X  530. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS  PLATE  XIV 


225]  UFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  105 


PLATE  XV 


•106  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [226 


EXPLANATION  OF  PLATE 
Gordius  robustus 
Tig.  115. — ^Nerve  fibre  entering  hypoderm  of  adult;  X  475. 
Fig.  116. — ^Early  stage  in  development  of  fibrous  cuticula;  slightly  later  stage  than  Fig.  35; 

X800. 
Fig.  117. — Fibrous  cuticula  about  half  developed;  X  430. 

Fig.  118. — Adult;  nerve  fibres  passing  from  neural  lamella  into  hypoderm;  X  450. 
Fig.  119. — ^Fibrous  cuticula;  development  almost  complete;  X  625. 
Fig.  120. — ^Nerve  fibres  in  hypoderm  of  adult;  X  435. 

Fig.  121. — Cross  section  thru  inner,  ventral  wall  of  prong  of  male;  shows  stout  bristle;  X  625. 
Fig.  122.— Section  slightly  outward  from  that  of  Fig.  121;  X  625. 
Fig.  123. — Section  thru  outer  wall  of  prong  of  same  specimen;  X  625- 
Fig.  124. — Old  specimen;  section  showing  extreme  degeneration  of  muscles;  X  430. 
Fig.  125. — Section  thru  old  specimen;  shows  b^inning  of  d^eneration  of  muscle  fibres;  X  430. 
Fig.  126. — ^End  of  muscle  cell  of  adult;  isolated  after  maceration  with  nitric  add;  X  625. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


115 


<PP^iO^S9 


'>^^2f^' 


116 


118 


120  W^- 


^'!>^^^^,,,  \|\ 


126 


J^i 


^kSS^ 


J- 124 


MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  XV 


227]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  7  107 


PLATE  XVI 


108  I LUNOIS  BIOLOGICAL  MONOGRAPHS  [228 


EXPLANATION  OF  PLATE 

Fig.  127. — Gordius  robustus,  tangential  section  of  hypodenn  of  young  specimen;  shows  nuclei 

and  nucleoli  as  well  as  radiating  canals;  X  800. 
Fig.  128. — G.  robustus,  tangential  section  thru  hypKxkrm  of  specimen  in  which  fibrous  cuticiila 

is  forming;  intercellular  bridges;  X  400. 
Fig.  129. — G.  robustus,  section  similar  to  that  of  Fig.  128;  nerve  fibre  in  hypoderm;  X  475. 
Fig.  130. — Paragordius  varius,  young  parasite  in  the  coiled  stage;  X  190. 
Fig.  131. — P.  varius,  very  yoimg  parasite;  side  view;  specimen  somewhat  flattened;  X  250. 
Fig.  132. — P.  varius,  anterior  end  of  adult;  side  view;  semi-transparent;  X  70. 
Fig.  133. — P.  varius,  posterior  end  of  adult  male;  ventral  view,  shows  rows  of  bristles;  X  70. 
Fig.  134. — P.  varius,  cross  section  of  host  containing  young  parasite;  X  37. 
Fig.  135. — P.  varius,  section  of  parasite  from  Fig.  134;  X  130. 
Fig.  136. — P.  varius,  cross  section  thru  middle  of  body  of  yoimg  specimen;  early  development 

of  gonads;  X  500. 
Fig.  137. — P.  varius,  spermatozoa;  smear  made  from  male;  X  800. 
Fig.  138. — P.  varius,  spermatozoa;  smear  made  from  seminal  receptacle  of  female;  X  800. 
Fig.  139. — P.  varius,  longitudinal  section  parallel  to  large  nerve  cells  in  ventral  cord;  shows 

bipolar  cells;  X  250. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


130 

GORDIUS  AND  PARAGORDIUS  PLATE  XVI 


229]  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  109 


PLATE  XVII 


110  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [230 


EXPLANATION  OF  PLATE 

Paragordius  varius 
Fig.  140. — Cross  section  thru  posterior  end  of  male  at  time  of  formation  of  adult  cuticula; 

X  365. 
Fig.  141. — Section  thru  posterior  region  of  young  male;  X  375. 
Fig.  142. — Section  of  same  specimen;  shows  sperm  ducts  entering  cloaca;  X  37S» 
Fig.  143. — Section  thru  cloaca  of  same  specimen;  X  375. 
Fig.  144. — Section  thru  same  specimen  at  base  of  prongs;  X  375. 
Fig.  145. — Yoimg  parasite;  cross  section;  X  500. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS         PLATE  XVII 


2311  LIFE  HISTORY  OF  GORDIUS  AND  PARAGORDIUS—MA  Y  111 


PLATE  XVIII 


112  ILLINOIS  BIOLOGICAL  MONOGRAPHS  1232 


EXPLANATION  OF  PLATE 
Paragordius  varius 
Fig.  146. — Cross  section  near  anterior  end  of  young  specimen;  X  500. 
Fig.  147. — Section  near  middle  of  body  of  same  specimen;  X  500. 
Fig.  148. — Section  near  posterior  end  of  young  male;  intestinal  diverticula  for  entrance  of 

sperm  ducts;  X  500. 
Fig.  149. — Section  thru  anal  region  of  same  male;  X  500. 
Fig.  150. — ^Young  specimen;  longitudinal  section  thru  anterior  end;  X  115. 
Fig.  151. — Part  of  Fig.  150;  shows  connection  between  intestine  and  proboscis;  X  500. 
Fig.  152. — ^Longitudinal  section  thru  anterior  region  of  female;  shows  ovarian  pockets  which 

appear  to  be  placed  irregularly  not  indicating  segmentation;  X  25. 
Fig.  153. — Sagittal  section  thru  anterior  end  of  young  specimen;  shows  esophagus;  X  150. 
Fig.  154. — ^Section  adjacent  to  that  of  Fig.  153;  X  150. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS       PLATE  XVIII 


2331  UFE  HISTORY  OP  GORDIUS  AND  PARAGORDIUS—MA  Y  113 


PLATE  XIX 


114  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [234 


EXPLANATION  OF  PLATE 
Paragordius  varius 
Fig.  155. — Section  thru  young  parasite;  X  500. 
Fig.  156. — ^Section  near  middle  of  body  of  young  parasite;  X  500. 
Fig.  157. — Section  near  middle  of  body  of  slightly  older  parasite;  X  500. 
Fig.  158. — Section  thru  middle  of  body  of  yoimg  female;  just  before  formation  of  adult  cuti- 

cula;  shows  formation  of  mesenteries;  X  400. 
Fig.  159. — Section  thru  female  at  beginning  of  formation  of  adult  cuticula;  mesenteries 

formed;  X  200. 
Fig.  160. — ^Longitudinal  section  thru  cuticula;  shows  areola  and  protoplasmic  strand;  X  400. 
Fig.  161. — ^Ventral  part  of  female  during  formation  of  adult  cuticula;  cross  section;  formation 

of  areolae;  X  500. 
Fig.  162. — Slightly  oblique  section  thru  anterior  end  of  young  parasite;  beginning  of  cephalic 

ganglion;  X  500. 
Fig.  163. — Cross  section  thru  cloacal  gland  of  female  at  the  time  the  larval  cuticula  is  shed; 

larval  cuticula  partly  loose;  X  150. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS  PLATE  XIX 


235]  LIFE  HISTOR Y  OF  GORDIUS  A ND  PARAGORDIUS—MA  Y  115 


PLATE  XX 


116  ILUNOIS  BIOLOGICAL  MONOGRAPHS  236 


EXPLANATION  OF  PLATE 
Paragordius  varius 

Fig.  164. — Section  thru  posterior  end  of  adult  male;  cloacal  ganglion  and  circular  muscles 

surrounding  the  sperm  ducts;  X  275. 
Fig.  165. — ^Longitudinal  section  thru  posterior  end  of  young  parasite;  shows  invaginated 

ectoderm  forming  intestinal  diverticula;  X  500. 
Fig.  166. — Cross  section  thru  anterior  region  of  specimen  with  adult  cuticula  nearly  complete; 

shows  cellular  projections  into  cuticula;  X  275. 
Fig.  167. — Cross  section  of  female  with  adult  cuticula  nearly  formed;  cellular  projections  and 

formation  of  areolae;  X  500. 
Fig.  168. — Sagittal  section  thru  upper  end  of  cloaca  of  female;  X  100. 
Fig.  169. — ^Early  stage  in  formation  of  cuticula;  areolae  very  small;  X  500. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  XX 


237]  LIFE  HISTORY  OF  GOKDIUS  AND  PARAGORDIUS—MA  Y  117 


PLATE  XXI 


118  ILUNOIS  BIOLOGICAL  MONOGRAPHS  ?23» 


EXPLANATION  OF  PLATE 
Paragordius  tarims 
Fig.  170. — Cross  section  thru  body  of  yoxmg  female;  ovarian  buds  not  yet  formed;  X  500. 
Fig.  171. — ^Frontal  section  thru  upper  end  of  cloaca  of  young  female;  X  115. 
Pig.  172. — Cross  section  thru  body  of  female;  dorsal  part  of  section;  be^nning  of  formation 

of  adult  cuticula;  structure  of  dorsal  part  of  mesenteries;  X500. 
Fig.  173. — ^Ventral  part  of  same  section  as  Fig.  172;  X  500. 
Fig.  174. — Cross  section  of  male  at  beginning  of  formation  of  adult  cuticula;  X  375. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  V 


MAY 


GORDIUS  AND  PARAGORDIUS 


PLATE  XXI 


